Add otlptext support for exponential histogram

[jmacd]

Description:
Add support for printing OTLP exponential histograms

Link to tracking Issue:
Fixes #4641

Testing:

I ran go test -v with a modified test to verify that the printed format (which the test does not actually validate for any data point) is correct.

The math equations used here are copied from open-telemetry/opentelemetry-go#2393 where they have been extensively tested.

[codecov]

Codecov Report

Merging #4642 (575ecf1) into main (60823e2) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #4642      +/-   ##
==========================================
+ Coverage   90.46%   90.50%   +0.04%     
==========================================
  Files         181      181              
  Lines       10611    10658      +47     
==========================================
+ Hits         9599     9646      +47     
  Misses        788      788              
  Partials      224      224              

Impacted Files	Coverage Δ
internal/otlptext/databuffer.go	100.00% <100.00%> (ø)

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