Checked if Operation Enabled in otlptracehttp before performing operation

[itssaharsh]

This PR adds the Enabled functionality to checked if the field is enabled before performing computational heavy work.
Tracked in #7800

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.7%. Comparing base (64f28b0) to head (297e0bd).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7881   +/-   ##
=====================================
  Coverage   81.7%   81.7%           
=====================================
  Files        304     304           
  Lines      23283   23287    +4     
=====================================
+ Hits       19032   19036    +4     
  Misses      3864    3864           
  Partials     387     387           

Files with missing lines	Coverage Δ
...e/otlptracehttp/internal/observ/instrumentation.go	100.0% <100.0%> (ø)

... and 3 files with indirect coverage changes

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[itssaharsh]

@MrAlias @dashpole any changes I should do in this pr?