Add the otlploghttp HTTP client

[MrAlias]

Without wanting to re-engineer the client this is almost entirely copied from the otlpmetrichttp client. The tests are also copied from there. The internal packages used there are flattened here. This is quite large, but given the copied nature and no clear way to break this up I have left it as is.

Part of #5057

[codecov]

Codecov Report

Attention: Patch coverage is 81.88976% with 23 lines in your changes are missing coverage. Please review.

Project coverage is 84.5%. Comparing base (94eb27f) to head (63a03f4).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5224     +/-   ##
=======================================
- Coverage   84.6%   84.5%   -0.1%     
=======================================
  Files        258     258             
  Lines      17224   17348    +124     
=======================================
+ Hits       14572   14675    +103     
- Misses      2349    2362     +13     
- Partials     303     311      +8     

Files	Coverage Δ
exporters/otlp/otlplog/otlploghttp/config.go	94.9% <100.0%> (ø)
exporters/otlp/otlplog/otlploghttp/client.go	82.5% <81.6%> (-17.5%)	⬇️

... and 1 file with indirect coverage changes

[pellared]

Side note: Reviewing it for me was quite easy for me given I was reading the same code this week when working on #5222 and #5221 😉 I think you did the right thing to flatten it out.