[CI] Sum up Azp unit test code coverage

[liushilongbuaa]

Description

1. Azp code coverage result is one of the six components by random. This PR summarized all six components test coverage.
2. Use one container to improve time efficiency.
3. Parameterize download artifacts.

Motivation and Context

Fix code coverage display error in azp.
Build in multiple containers didn't improve time efficiency.

How Has This Been Tested?

Check code coverage result in Checks/azure pipeline

Additional Information (Optional)

[qiluo-msft]

LGTM. Wait PR build result.

[liushilongbuaa]

LGTM. Wait PR build result.

result is here: https://dev.azure.com/mssonic/build/_build/results?buildId=26985&view=results
Because I have changed PR check yaml file from 7 parallel jobs into 1 serial job, PR check seems not finished. But actually it is finished.

[liushilongbuaa]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[liushilongbuaa]

PR checker will not pass at all. Because 7 old jobs is replaced by 1 new job.
why I changed 7 jobs to 1 job? Because 7 parallel jobs didn't save time. They waste a lot of time downloading the same container and same artifacts.

[qiluo-msft]

The PR checkers are actually passed. Check the Checks page. I will override and merge.