Adds Baggage.getEntry(String key)

[breedx-splk]

Resolves #6729.

This prevents users from having to go through asMap() in order to fetch the metadata for a given BaggageEntry.

[trask]

makes sense to me

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.09%. Comparing base (a6a9acb) to head (5d1fd65).
Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
...ain/java/io/opentelemetry/api/baggage/Baggage.java	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@ Coverage Diff @@ ## main #6765 +/- ## ============================================ + Coverage 90.02% 90.09% +0.06%  - Complexity 6488 6544 +56  ============================================ Files 719 728 +9 Lines 19587 19702 +115 Branches 1931 1935 +4 ============================================ + Hits 17634 17750 +116  + Misses 1354 1349 -5  - Partials 599 603 +4 

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.