Introduce code coverage job for matrix build (#333)

## Description

Introduce a unified job to process and publish code coverage data.

- [ ] Impacts functionality?
- [ ] Impacts security?
- [ ] Breaking change?
- [ ] Includes tests?
- [ ] Includes documentation?

## How This Was Tested

Tested in test pipeline

## Integration Instructions

N/A

.azurepipelines/Matrix-Build-Job.yml

@@ -94,3 +94,14 @@ jobs:
       extra_install_step: ${{ parameters.extra_install_step }}
       tool_chain_tag: ${{ parameters.tool_chain_tag }}
       install_tools: ${{ eq(parameters.container_image, '') }}
+
+- job: PublishCoverage
+  dependsOn: Build
+  workspace:
+    clean: all
+
+  pool:
+    vmImage: 'windows-latest'
+
+  steps:
+    - template: Steps/PublishCodeCoverage.yml@mu_devops

BaseTools/Plugin/HostBasedUnitTestRunner/HostBasedUnitTestRunner.py

@@ -193,6 +193,9 @@ def gen_code_coverage_gcc(self, thebuilder):
         if os.path.isfile(f"{workspace}/Build/coverage.xml"):
             os.remove(f"{workspace}/Build/coverage.xml")
         ret = RunCmd("lcov_cobertura",f"{workspace}/Build/all-coverage.info --excludes ^.*UnitTest\|^.*MU\|^.*Mock\|^.*DEBUG -o {workspace}/Build/coverage.xml")
+        if ret != 0:
+            logging.error("UnitTest Coverage: Failed generate all coverage XML.")
+            return 1
 
         return 0