Base set of Azure DevOps pipeline library source (#3021)

* Base set of Azure DevOps pipeline library source

A base set of yaml files to orchestrate the build and testing of ROCm compiler and runtime components in an Azure DevOps project.

* Use hipcc in llvm-project, also build OpenCL runtime.

* Adding llvm-lit tests to llvm-project pipeline.

Added comgr ctest as well.

* rocm-cmake unit testing in pipeline

* Pipeline changes corresponding to 6.1 release

.azuredevops/variables-global.yml

@@ -0,0 +1,13 @@
+# specify non-secret global variables reused across pipelines here
+
+variables:
+- name: CI_ROOT_PATH
+  value: /.azuredevops
+- name: CI_COMPONENT_PATH
+  value: ${{ variables.CI_ROOT_PATH }}/components
+- name: CI_TEMPLATE_PATH
+  value: ${{ variables.CI_ROOT_PATH }}/templates
+- name: LOW_END_BUILD_POOL
+  value: ubuntu-22.04
+- name: HIGH_END_BUILD_POOL
+  value: rocm-ci_build_pool