Migrate splunk ta otel collector to golang

[hughesjj]

This migrates the addon Splunk_TA_otel to a golang version, which should be easier to maintain long term.

The idea is we could get rid of maintaining two scripts (the .cmd and .sh), and instead vend binaries. This also makes signal passing much easier to the Otel TA.

Even better would be to modify cmd/otelcol to vend an additional binary that waits for modinput-like xml on startup, but we decided against this when talking about such a ~year ago

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.00%. Comparing base (4921a1b) to head (45acec6).

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6526       +/-   ##
===========================================
+ Coverage   33.27%   44.00%   +10.72%     
===========================================
  Files         365      376       +11     
  Lines       26044    26459      +415     
===========================================
+ Hits         8667    11644     +2977     
+ Misses      16465    13984     -2481     
+ Partials      912      831       -81     

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[pjanotti]

Even better would be to modify cmd/otelcol to vend an additional binary that waits for modinput-like xml on startup, but we decided against this when talking about such a ~year ago

I think a dedicated cmd as the best option in general, not to mix with the normal otelcol but a separate cmd. Anyway, there will be challenges because there are is more than a very thin wrapper under cmd/otelcol