Change OTLP/HTTP default port from 4317 to 4318

[lalitb]

As per the changes in the specs: open-telemetry/opentelemetry-specification#1970
This could be the BREAKING change, but since the collector never moved to 4317 for grpc-http ( as per its commit history ), it shouldn't affect many customers.

Note: this is still in process of reservation with IANA (open-telemetry/opentelemetry-specification#1970 (comment) )

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1018 (cd3f475) into main (096c08b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1018   +/-   ##
=======================================
  Coverage   95.41%   95.41%           
=======================================
  Files         161      161           
  Lines        6833     6833           
=======================================
  Hits         6519     6519           
  Misses        314      314