Switch stargz over to cri registry config_path

[brandond]

Proposed Changes

Migrate the stargz CRI registry config over to config_path, same as the core containerd CRI config.

This should have been done as part of #8973 but I didn't realize stargz already supported it, ref: containerd/stargz-snapshotter#331

Types of Changes

tech debt

Verification

Note use of config_path under [plugins."io.containerd.snapshotter.v1.stargz".registry] in config.toml, when stargz snapshotter is enabled.

Testing

yes

Linked Issues

• Support containerd config_path for stargz snapshotter #9976

User-Facing Change

Further Comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.53%. Comparing base (81cd630) to head (e07466e).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9977      +/-   ##
==========================================
- Coverage   49.63%   43.53%   -6.10%     
==========================================
  Files         158      158              
  Lines       14017    14017              
==========================================
- Hits         6958     6103     -855     
- Misses       5755     6750     +995     
+ Partials     1304     1164     -140     

Flag	Coverage Δ
e2etests	36.41% <ø> (-9.73%)	⬇️
inttests	37.06% <ø> (+<0.01%)	⬆️
unittests	16.56% <ø> (ø)

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