Pass CI workflow inputs through environment variables (#39717)

## Why

Embedding reusable-workflow inputs directly in shell scripts can cause their
contents to be interpreted as shell syntax.

## What changed

- Export the Rust nextest target, profile, and test-thread inputs as environment
  variables before using them in Bash commands and paths.
- Pass the MSVC target and host architecture to PowerShell through environment
  variables.

GitOrigin-RevId: f96bbeeb7b556022e4bdea9db384a88f925050bf

.github/actions/setup-msvc-env/action.yml

@@ -14,4 +14,7 @@ runs:
   steps:
     - name: Expose MSVC SDK environment
       shell: pwsh
-      run: '& "$env:GITHUB_ACTION_PATH/setup-msvc-env.ps1" -Target "${{ inputs.target }}" -HostArch "${{ inputs.host-arch }}"'
+      env:
+        HOST_ARCH: ${{ inputs.host-arch }}
+        TARGET: ${{ inputs.target }}
+      run: '& "$env:GITHUB_ACTION_PATH/setup-msvc-env.ps1" -Target "$env:TARGET" -HostArch "$env:HOST_ARCH"'