Set declarative config default OTLP protocol to http/protobuf

[jack-berg]

This comment from the code explains the motivation behind this:

NOTE: The default OTLP protocol is different for declarative config than for env var / system property based config. This is intentional. OpenTelemetry changed the default protocol recommendation from grpc to http/protobuf, but the autoconfigure's env var / system property based config did not update to reflect this before stabilizing, and changing is a breaking change requiring a major version bump. Declarative config is not yet stable and therefore can switch to the current default recommendation, which aligns also aligns with the behavior of the OpenTelemetry Java Agent 2.x+.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.88%. Comparing base (537f5c4) to head (a1e5def).
Report is 3 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6800      +/-   ##
============================================
- Coverage     90.11%   89.88%   -0.23%     
+ Complexity     6545     6539       -6     
============================================
  Files           728      728              
  Lines         19702    19702              
  Branches       1935     1935              
============================================
- Hits          17755    17710      -45     
- Misses         1347     1390      +43     
- Partials        600      602       +2     

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