ADO CI, rm variables (#213)

This pull request updates the CI pipeline configuration in
`.azdo/ci.yaml` to simplify variable usage and streamline build, test,
and packaging steps. The main changes focus on removing unused
variables, switching to direct script commands for testing and
packaging, and ensuring consistent use of the `Release` configuration.

**Pipeline configuration simplification:**

* Removed the `variables` section (`buildConfiguration`,
`workingDirectory`) to reduce complexity and hardcoded the `Release`
configuration in build/test/pack steps.

**Build, test, and packaging process updates:**

* Changed the `dotnet build` step to use the `Release` configuration
directly, eliminating reliance on pipeline variables.
* Replaced the NuGet pack task (`DotNetCoreCLI@2`) with a direct `dotnet
pack` script command, improving clarity and maintainability.
* Added an explicit `dotnet test` step to run tests after building,
ensuring code quality before packaging.
* Updated the pack step to use the output directory and symbol package
format directly in the script command for consistency.

Author: rido-min

.azdo/ci.yaml

@@ -7,10 +7,6 @@ pr:
 pool:
   vmImage: 'ubuntu-22.04'
 
-variables:
-  buildConfiguration: 'Release'
-  workingDirectory: 'botbuilder-dotnet'
-
 stages:
 - stage: Build_Test_Pack
   jobs:
@@ -27,22 +23,14 @@ stages:
       - script: dotnet restore 
         displayName: 'Restore'
 
-      - script: dotnet build --configuration $(buildConfiguration) --no-restore
+      - script: dotnet build --no-restore --configuration Release
         displayName: 'Build'
-      
-      - task: DotNetCoreCLI@2
-        displayName: 'Pack NuGet Packages'
-        inputs:
-          command: pack
-          packagesToPack: 'Microsoft.Teams.sln'
-          packDirectory: '$(Build.ArtifactStagingDirectory)'
-          includesymbols: false
-          nobuild: true
-          configuration: '$(buildConfiguration)'
-          versioningScheme: 'byEnvVar'
-          versionEnvVar: 'Version'
-          buildProperties: 'SymbolPackageFormat=snupkg'
 
+      - script: dotnet test --no-build --configuration Release
+        displayName: 'Test'
+
+      - script: dotnet pack --no-build -o $(Build.ArtifactStagingDirectory) /p:SymbolPackageFormat=snupkg --configuration Release
+        displayName: 'Pack'
 
       - task: NuGetCommand@2
         displayName: 'Push NuGet Packages'