Add HttpSenderProvider SPI

[jack-berg]

Followup to #5505. Related to #5351.

This adds a new HttpSenderProvider SPI interface for configuring different HttpSender implementations.

It also splits out the OkHttpSender into a new artifact opentelemetry-exporter-http-sender-okhttp.

Another followup PR will define a JDK based HttpSender in a new artifact opentelemetry-exporter-http-sender-jdk.

[codecov]

Codecov Report

Patch coverage: 92.85% and project coverage change: +0.02 🎉

Comparison is base (f89fc05) 91.38% compared to head (73a1ceb) 91.40%.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5533      +/-   ##
============================================
+ Coverage     91.38%   91.40%   +0.02%     
- Complexity     4959     4963       +4     
============================================
  Files           549      550       +1     
  Lines         14563    14569       +6     
  Branches       1356     1358       +2     
============================================
+ Hits          13308    13317       +9     
+ Misses          868      866       -2     
+ Partials        387      386       -1     

Impacted Files	Coverage Δ
...xporter/http/okhttp/internal/OkHttpHttpSender.java	98.43% <ø> (ø)
...ry/exporter/internal/http/HttpExporterBuilder.java	92.15% <91.66%> (+1.45%)	⬆️
...http/okhttp/internal/OkHttpHttpSenderProvider.java	100.00% <100.00%> (ø)

... and 10 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[jack-berg]

/easycla

[brunobat]

Thanks @jack-berg !