[smithy-rs] Add support for operationContextParams Endpoints trait (#3755)

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
<!--- If it fixes an open issue, please link to the issue here -->
We have to support the new [`operationContextParams`
trait](https://smithy.io/2.0/additional-specs/rules-engine/parameters.html#smithy-rules-operationcontextparams-trait)
for endpoint resolution. This trait specifies JMESPath expressions for
selecting parameter data from the operation's input type.

## Description
<!--- Describe your changes in detail -->
* Add codegen support for the [JMESPath
`keys`](https://jmespath.org/specification.html#keys) function (required
by the trait
[spec](https://smithy.io/2.0/additional-specs/rules-engine/parameters.html#smithy-rules-operationcontextparams-trait))
* Add codegen support for the trait itself. This is achieved by
generating `get_param_name` functions for each param specified in
`operationContextParams`. These functions pull the data out of the input
object and it is added to the endpoint params in the
`${operationName}EndpointParamsInterceptor`

## Testing
<!--- Please describe in detail how you tested your changes -->
<!--- Include details of your testing environment, and the tests you ran
to -->
<!--- see how your change affects other areas of the code, etc. -->
Updated the existing test suite for JMESPath codegen to test the `keys`
function. Updated the existing EndpointsDecoratorTest with an
`operationContextParams` trait specifying one param of each supported
type to test the codegen.

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

Author: landonxjames

sdk/accessanalyzer/src/operation/apply_archive_rule.rs

@@ -245,6 +245,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for ApplyArchiveR
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `ApplyArchiveRuleError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/cancel_policy_generation.rs

@@ -249,6 +249,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for CancelPolicyG
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `CancelPolicyGenerationError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/check_access_not_granted.rs

@@ -244,6 +244,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for CheckAccessNo
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `CheckAccessNotGrantedError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/check_no_new_access.rs

@@ -236,6 +236,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for CheckNoNewAcc
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `CheckNoNewAccessError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/check_no_public_access.rs

@@ -244,6 +244,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for CheckNoPublic
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `CheckNoPublicAccessError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/create_access_preview.rs

@@ -253,6 +253,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for CreateAccessP
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `CreateAccessPreviewError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/create_analyzer.rs

@@ -245,6 +245,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for CreateAnalyze
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `CreateAnalyzerError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/create_archive_rule.rs

@@ -256,6 +256,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for CreateArchive
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `CreateArchiveRuleError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/delete_analyzer.rs

@@ -265,6 +265,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for DeleteAnalyze
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `DeleteAnalyzerError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]

sdk/accessanalyzer/src/operation/delete_archive_rule.rs

@@ -282,6 +282,9 @@ impl ::aws_smithy_runtime_api::client::interceptors::Intercept for DeleteArchive
     }
 }
 
+// The get_* functions below are generated from JMESPath expressions in the
+// operationContextParams trait. They target the operation's input shape.
+
 /// Error type for the `DeleteArchiveRuleError` operation.
 #[non_exhaustive]
 #[derive(::std::fmt::Debug)]