OpenTelemetry fixes from PR (Azure#2888)

Fixes Azure#2853 
Fixes Azure#2850 
Fixes Azure#2827 

Fixes to OpenTelemetry issues raised by @heaths from the OpenTelemetry
PR.

---------

Co-authored-by: Copilot <[email protected]>

Author: LarryOsterman

Cargo.lock

@@ -86,9 +86,9 @@ For the Rust implementation, if a tracer provider is configured, ALL http operat
 
 ## Implementation details
 
-To provide for requirement #1, if a customer provides a value for the `azure_core::ClientOptions::request_instrumentation` structure, the Azure Core HTTP pipeline will add a `PublicApiInstrumentationPolicy` to the pipeline which is responsible for creating the public API outer span.
+To provide for requirement #1, if a customer provides a value for the `azure_core::ClientOptions::instrumentation` structure, the Azure Core HTTP pipeline will add a `PublicApiInstrumentationPolicy` to the pipeline which is responsible for creating the public API outer span.
 
-To provide for requirement #2, if a customer provides a `azure_core::ClientOptions::request_instrumentation` the `azure_core` HTTP pipeline will add a `RequestInstrumentationPolicy` to the pipeline which is responsible for creating the required HTTP request span to the pipeline.
+To provide for requirement #2, if a customer provides a `azure_core::ClientOptions::instrumentation` the `azure_core` HTTP pipeline will add a `RequestInstrumentationPolicy` to the pipeline which is responsible for creating the required HTTP request span to the pipeline.
 
 This implementation means that operations like Long Running Operations (Pollers) and Pageable Operations (Pagers) will all have a Public API span created by the `PublicApiInstrumentationPolicy` and a HTTP Request span created by the `RequestInstrumentationPolicy`.
 
@@ -218,7 +218,7 @@ pub fn new(
         vec!["https://vault.azure.net/.default"],
     ));
 +    let tracer =
-+    if let Some(tracer_options) = &options.client_options.request_instrumentation {
++    if let Some(tracer_options) = &options.client_options.instrumentation {
 +        tracer_options
 +            .tracer_provider
 +            .as_ref()

doc/distributed-tracing-for-rust-service-clients.md

@@ -5,7 +5,7 @@ use std::sync::Arc;
 
 /// Policy options to enable distributed tracing.
 #[derive(Clone, Debug, Default)]
-pub struct RequestInstrumentationOptions {
+pub struct InstrumentationOptions {
     /// Set the tracer provider for distributed tracing.
     pub tracer_provider: Option<Arc<dyn crate::tracing::TracerProvider>>,
 }