Add ability to include swift versions

In some cases, such as swiftly, there's only one particular version
of swift that is being targeted at a time. It's problematic trying
to exclude all of the others in the default list, and have to adjust
when the workflow gets changed, making sure to exclude any additions.
Add the ability for a repo like swiftly to set the list to explicit
version(s) instead of excluding everything except that one version.

Author: cmcgee1024

.github/workflows/swift_package_test.yml

@@ -3,6 +3,10 @@ name: Swift Linux Matrix
 on:
   workflow_call:
     inputs:
+      linux_swift_versions:
+        type: string
+        description: "Include Linux Swift version list (JSON)"
+        default: "[\"5.8\", \"5.9\", \"5.10\", \"6.0\", \"nightly-main\", \"nightly-6.0\"]"
       linux_exclude_swift_versions:
         type: string
         description: "Exclude Linux Swift version list (JSON)"
@@ -11,6 +15,10 @@ on:
         type: string
         description: "Linux OS version list (JSON)"
         default: "[\"jammy\"]"
+      windows_swift_versions:
+        type: string
+        description: "Include Windows Swift version list (JSON)"
+        default: "[\"5.9\", \"6.0\", \"nightly\", \"nightly-6.0\"]"
       windows_exclude_swift_versions:
         type: string
         description: "Exclude Windows Swift version list (JSON)"
@@ -57,7 +65,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        swift_version: ['5.8', '5.9', '5.10', '6.0', 'nightly-main', 'nightly-6.0']
+        swift_version: ${{ fromJson(inputs.linux_swift_versions) }}
         os_version: ${{ fromJson(inputs.linux_os_versions) }}
         exclude:
           - ${{ fromJson(inputs.linux_exclude_swift_versions) }}
@@ -87,7 +95,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        swift_version: ['5.9', '6.0', 'nightly', 'nightly-6.0']
+        swift_version: ${{ fromJson(inputs.windows_swift_versions) }}
         exclude:
           - ${{ fromJson(inputs.windows_exclude_swift_versions) }}
     steps: