docs: make crate READMEs consistent

[cijothomas]

Revives #3074 to normalize the crate README structure (Overview / What does this crate contain? / Getting started / Release Notes / Supported Rust Versions). Fixes #1306.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.2%. Comparing base (4607956) to head (3020058).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3583   +/-   ##
=====================================
  Coverage   83.2%   83.2%           
=====================================
  Files        130     130           
  Lines      28246   28246           
=====================================
  Hits       23506   23506           
  Misses      4740    4740           

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[cijothomas]

@utpilla please re-review. Thanks!

[lalitb]

Nit - I think these two links should be in all the READMEs. As of now they are missing for opentelemetry-appender-tracing and opentelemetry-jaeger-propagator.

[lalitb]

LGTM. For future direction, it may be worth considering a small template/marker-based approach for the repeated README sections. Each crate README could still keep its crate-specific content, but shared sections like Overview and Supported Rust Versions could come from one source to avoid drift over time.