feature: save context between calls

[TerryHowe]

What this PR does / why we need it:

This change saves authentication cache between calls so ORAS go scripting will auth once for most usages.

I created a test application to functional test this and it only authenticates the once.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 87.27%. Comparing base (7383f87) to head (46fffb6). :warning: Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/oras/internal/option/remote.go	80.00%	4 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1923      +/-   ##
==========================================
- Coverage   87.33%   87.27%   -0.07%     
==========================================
  Files         143      143              
  Lines        5535     5554      +19     
==========================================
+ Hits         4834     4847      +13     
- Misses        415      421       +6     
  Partials      286      286              

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