feat: add `--template` and support `--format go-template=TEMPLATE` experience

[qweeah]

What this PR does / why we need it: This PR implements latest change in #1199

Please check the following list:

• [x] 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[bot]]

Codecov Report

Attention: Patch coverage is 95.16129% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 85.02%. Comparing base (96d64da) to head (70cd7f0).

Files	Patch %	Lines
cmd/oras/internal/display/handler.go	91.11%	1 Missing and 3 partials :warning:
cmd/oras/root/discover.go	86.66%	1 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1377      +/-   ##
==========================================
+ Coverage   84.91%   85.02%   +0.10%     
==========================================
  Files         107      107              
  Lines        3739     3806      +67     
==========================================
+ Hits         3175     3236      +61     
- Misses        336      341       +5     
- Partials      228      229       +1     

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