refactor: simplify track reader manager and messenger use

[TerryHowe]

What this PR does / why we need it:

If we just pass the messenger to reader, it will be a lot easier to test these packages.

Partial: #1461
Partial: #1449

[codecov]

Codecov Report

Attention: Patch coverage is 87.00000% with 13 lines in your changes missing coverage. Please review.

Project coverage is 84.37%. Comparing base (8a31d9b) to head (e50ebfd).
Report is 25 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/oras/internal/display/status/track/target.go	64.70%	4 Missing and 2 partials ⚠️
cmd/oras/root/blob/fetch.go	66.66%	3 Missing and 1 partial ⚠️
cmd/oras/root/blob/push.go	72.72%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1474      +/-   ##
==========================================
+ Coverage   84.34%   84.37%   +0.02%     
==========================================
  Files         120      121       +1     
  Lines        5449     5509      +60     
==========================================
+ Hits         4596     4648      +52     
- Misses        606      612       +6     
- Partials      247      249       +2     

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[github-actions]

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]

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.

[TerryHowe]

I think I still want to pull something out of this.