[devops] Add 'net8.0' and 'release-test/*' as release branches. (#16383)

This is a follow-up to dbcf1cadf8.

tools/devops/automation/templates/main-stage.yml

@@ -230,7 +230,7 @@ stages:
 
 # .NET Release Prep and VS Insertion Stages, only execute them when the build comes from an official branch and is not a schedule build from OneLoc
 # setting the stage at this level makes the graph of the UI look better, else the lines overlap and is not clear.
-- ${{ if and(ne(variables['Build.Reason'], 'Schedule'), or(eq(variables['Build.SourceBranch'], 'refs/heads/main'), startsWith(variables['Build.SourceBranch'], 'refs/heads/release/'), eq(variables['Build.SourceBranch'], 'refs/heads/net7.0'), eq(parameters.forceInsertion, true))) }}:
+- ${{ if and(ne(variables['Build.Reason'], 'Schedule'), or(eq(variables['Build.SourceBranch'], 'refs/heads/main'), startsWith(variables['Build.SourceBranch'], 'refs/heads/release/'), startsWith(variables['Build.SourceBranch'], 'refs/heads/release-test/'), eq(variables['Build.SourceBranch'], 'refs/heads/net7.0'), eq(variables['Build.SourceBranch'], 'refs/heads/net8.0'), eq(parameters.forceInsertion, true))) }}:
   - template: ./release/vs-insertion-prep.yml
     parameters:
       dependsOn: