refactor: Disable CodeQL in test pipelines (microsoft#22802)

## Description

Disables the auto-injection of CodeQL tasks in our test pipelines. The
CodeQL tasks always "fail" (the ADO step still succeeds but the task
can't find source code so it can't run CodeQL and logs warnings) in the
test pipelines for which we don't checkout the repo, which is the case
for our test pipelines.
[Example](https://dev.azure.com/fluidframework/internal/_build/results?buildId=300062&view=logs&j=26483432-40f5-552c-5792-70aed8cde738&t=fb288d9b-a668-57e8-da86-3cec1930f710&l=55)
(msft internal). The task itself says that it should only run for build
pipelines (where source code exists).

tools/pipelines/test-dds-stress.yml

@@ -25,6 +25,9 @@ variables:
 - name: absolutePathToTelemetryGenerator
   value: $(Build.SourcesDirectory)/tools/telemetry-generator
   readonly: true
+# This is a test pipeline, not a build one, so we don't need to run CodeQL tasks
+- name: DisableCodeQL
+  value: true
 
 parameters:
 - name: packages

tools/pipelines/test-perf-benchmarks.yml

@@ -84,6 +84,9 @@ variables:
   - name: pipelineIdentifierForTelemetry
     value: 'PerformanceBenchmark'
     readonly: true
+  # This is a test pipeline, not a build one, so we don't need to run CodeQL tasks
+  - name: DisableCodeQL
+    value: true
 
 lockBehavior: sequential
 stages:

tools/pipelines/test-real-service-stress.yml

@@ -33,6 +33,9 @@ variables:
 - name: pipelineIdentifierForTelemetry
   value: 'RealStressService'
   readonly: true
+# This is a test pipeline, not a build one, so we don't need to run CodeQL tasks
+- name: DisableCodeQL
+  value: true
 
 lockBehavior: sequential
 stages:

tools/pipelines/test-real-service.yml

@@ -33,6 +33,9 @@ variables:
 - name: pipelineIdentifierForTelemetry
   value: 'EndToEndTests'
   readonly: true
+# This is a test pipeline, not a build one, so we don't need to run CodeQL tasks
+- name: DisableCodeQL
+  value: true
 
 lockBehavior: sequential
 stages:

tools/pipelines/test-service-clients.yml

@@ -33,6 +33,9 @@ variables:
 - name: pipelineIdentifierForTelemetry
   value: 'ServiceClientsEndToEndTests'
   readonly: true
+# This is a test pipeline, not a build one, so we don't need to run CodeQL tasks
+- name: DisableCodeQL
+  value: true
 
 stages:
   # Run Azure Client FRS Tests

tools/pipelines/test-stability.yml

@@ -142,6 +142,9 @@ variables:
   value: 1
 - name: pnpmStorePath
   value: $(Pipeline.Workspace)/.pnpm-store
+# This is a test pipeline, not a build one, so we don't need to run CodeQL tasks
+- name: DisableCodeQL
+  value: true
 
 stages:
   - ${{ each stageName in parameters.stageNames }}: