Add skip-lts-prepass input to optimize .NET SDK installation process (#791)

- Introduced `skip-lts-prepass` input to allow users to skip the LTS runtime pre-pass during installation.
- Updated documentation to explain the new input and its usage.
- Enhanced tests to verify the behavior of the `skip-lts-prepass` functionality.

Co-authored-by: chiranjib-swain <chiranjib-swain@github.com>

action.yml

@@ -14,6 +14,10 @@ inputs:
   dotnet-channel:
     description: 'Optional channel for the installation. The possible values are: STS, LTS, A.B (e.g. 8.0), A.B.Cxx (e.g. 8.0.1xx, available since 5.0). To be used with "dotnet-version: latest".'
     required: false
+  skip-lts-prepass:
+    description: 'Optional. When true, skips the LTS runtime pre-pass and installs only the requested dotnet-version. Default: false.'
+    required: false
+    default: false
   global-json-file:
     description: 'Optional global.json location, if your global.json isn''t located in the root of the repo.'
     required: false