refactor: add handlers to manifest push commmand

[wangxiaoxuan273]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Part of #1542

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]

Codecov Report

Attention: Patch coverage is 81.39535% with 8 lines in your changes missing coverage. Please review.

Project coverage is 84.33%. Comparing base (840f82e) to head (5c3721a).

Files with missing lines	Patch %	Lines
cmd/oras/root/manifest/push.go	40.00%	2 Missing and 4 partials ⚠️
cmd/oras/internal/display/metadata/discard.go	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1555      +/-   ##
==========================================
+ Coverage   84.30%   84.33%   +0.03%     
==========================================
  Files         120      120              
  Lines        5416     5446      +30     
==========================================
+ Hits         4566     4593      +27     
- Misses        604      606       +2     
- Partials      246      247       +1     

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[qweeah]

@wangxiaoxuan273 Can you help resolve the conflict?

[shizhMSFT]

Please follow @qweeah's comments

[qweeah]

No need to reset printer.Verbose in the command code, remove opts.Printer.Verbose = opts.verbose && !opts.OutputDescriptor in the RunE

[qweeah]

LGTM