Update Azure Pipelines to split push into multiple jobs

[tomqin93]

What this PR does / why we need it:
This PR splits Docker image push into multiple jobs to speed up build, also updates README badges to display stages instead of just one
Will this PR make the community happier?
Yes
Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

Release note:

- updates Azure Pipelines to split push into multiple jobs
- exclude README from builds
- update README.md with separated build stages 

[codecov]

Codecov Report

Merging #247 (c571e1d) into main (abd2141) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #247   +/-   ##
=======================================
  Coverage   21.85%   21.85%           
=======================================
  Files           8        8           
  Lines         828      828           
=======================================
  Hits          181      181           
  Misses        628      628           
  Partials       19       19           

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