CHORE: Renamed test pipeline and enabled main branch triggers (#66)

ADO Task ID:
[AB#37623](https://sqlclientdrivers.visualstudio.com/c6d89619-62de-46a0-8b46-70b92a84d85e/_workitems/edit/37623)

This pull request updates pipeline configurations to streamline triggers
and improve naming conventions. The changes focus on ensuring pipelines
are triggered only on relevant events and enhancing clarity in pipeline
naming.

Updates to pipeline triggers:

*
[`eng/pipelines/build-whl-pipeline.yml`](diffhunk://#diff-a871d64acfb78366b4b077045db53551c2df7d622854569f5f6780ad2ec6f911L4-L9):
Modified the trigger to activate only on merges to the `main` branch,
removing the `dev` branch from the trigger list.

Enhancements to pipeline naming:

* Renamed `eng/pipelines/test-pipeline.yml` to
`eng/pipelines/pr-validation-pipeline.yml` and updated its name within
the file for consistency.

Author: bewithgaurav

eng/pipelines/build-whl-pipeline.yml

@@ -1,12 +1,11 @@
 # Pipeline name shown in ADO UI
 name: build-whl-pipeline
 
-# Trigger the pipeline on pushes to these branches
+# Trigger the pipeline on merge to main branch only
 trigger:
   branches:
     include:
       - main
-      - dev
 
 # Use Microsoft-hosted Windows VM
 pool:

eng/pipelines/test-pipeline.yml eng/pipelines/pr-validation-pipeline.ymleng/pipelines/test-pipeline.yml renamed to eng/pipelines/pr-validation-pipeline.yml

@@ -1,4 +1,10 @@
-name: test-pipeline
+name: pr-validation-pipeline
+
+# Trigger the pipeline on merge to main branch
+trigger:
+  branches:
+    include:
+      - main
 
 jobs:
 - job: PytestOnWindows