adding identity token as an approximate alias of password

[sbdtu5498]

What this PR does / why we need it: These changes make the identity token an approximate alias of a password. The underlying implementation still depends on the password implementation, but a few cases to handle exceptions and errors have been added, thus technically speaking, it is not an alias but can be considered an approximate alias to enhance UX in terms of user's understandability.

Which issue(s) this PR fixes Fixes #742

Please check the following list:

• [ ] Does the affected code have corresponding tests, e.g. unit test, E2E test?
• [x] Does this change require a documentation update?
• [ ] Does this introduce breaking changes that would require an announcement or bumping the major version?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 53.65854% with 19 lines in your changes are missing coverage. Please review.

Project coverage is 81.63%. Comparing base (5608eeb) to head (976db98).

Files	Patch %	Lines
cmd/oras/internal/option/remote.go	53.84%	8 Missing and 4 partials :warning:
cmd/oras/root/login.go	53.33%	4 Missing and 3 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1040      +/-   ##
==========================================
- Coverage   81.97%   81.63%   -0.35%     
==========================================
  Files          83       83              
  Lines        3995     4024      +29     
==========================================
+ Hits         3275     3285      +10     
- Misses        497      509      +12     
- Partials      223      230       +7     

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[TerryHowe]

Where is this going? Be nice to get this out.

[github-actions[bot]]

This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 30 days.

[FeynmanZhou]

@sbdtu5498 Will you be able to continue to work on this PR? It has been stale for a long time and might be closed if no follow-ups on it in a few weeks.

[github-actions[bot]]

This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 30 days.

[github-actions[bot]]

This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 30 days.

[shizhMSFT]

Succeeded and closed by #1294