test: make e2e coverage data in action

[qweeah]

What this PR does / why we need it:
As a follow-up of #924, this PR moves the action of coverage data generation out of e2e run script.
Also added some e2e specs to validate the changes.

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[codecov-commenter]

Codecov Report

Merging #926 (cffe449) into main (9d7edb9) will increase coverage by 0.21%.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##             main     #926      +/-   ##
==========================================
+ Coverage   80.09%   80.30%   +0.21%     
==========================================
  Files          53       53              
  Lines        2853     2853              
==========================================
+ Hits         2285     2291       +6     
+ Misses        388      383       -5     
+ Partials      180      179       -1     

see 4 files with indirect coverage changes

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[shizhMSFT]

LGTM