refactor!: modernize Reference

[shizhMSFT]

What this PR does / why we need it

Modernize RemoteReference to Reference witht dotnet / C# features.

Which issue(s) this PR resolves / fixes

Resolve partially #91

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: 34 lines in your changes are missing coverage. Please review.

Comparison is base (538d214) 72.35% compared to head (964d235) 71.32%.

Files	Patch %	Lines
src/OrasProject.Oras/Registry/Reference.cs	69.30%	26 Missing and 5 partials ⚠️
src/OrasProject.Oras/Registry/Remote/Repository.cs	88.23%	1 Missing and 1 partial ⚠️
src/OrasProject.Oras/Registry/Remote/Registry.cs	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #93      +/-   ##
==========================================
- Coverage   72.35%   71.32%   -1.04%     
==========================================
  Files          35       35              
  Lines        1013     1001      -12     
  Branches       93       97       +4     
==========================================
- Hits          733      714      -19     
- Misses        229      237       +8     
+ Partials       51       50       -1     

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[sajayantony]

Are you planning to bring up the code coverage for this? The changes are really good.

[shizhMSFT]

Are you planning to bring up the code coverage for this? The changes are really good.

The purpose of this set of PRs are to modernize the code (i.e. focusing on interfaces). Perf improvement and code coverage will be future works.

[Wwwsylvia]

LGTM