Switch version from function to string in runtime

[carsontham]

Fixes part of #8272
Updated instrumentation/runtime version from a function to a string constant

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.2%. Comparing base (0948681) to head (7fe7cc5).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #8349     +/-   ##
=======================================
- Coverage   82.3%   82.2%   -0.1%     
=======================================
  Files        184     183      -1     
  Lines      13768   13766      -2     
=======================================
- Hits       11333   11320     -13     
- Misses      2030    2041     +11     
  Partials     405     405             

Files with missing lines	Coverage Δ
instrumentation/runtime/producer.go	86.2% <100.0%> (ø)
instrumentation/runtime/runtime.go	73.3% <100.0%> (ø)

... and 1 file with indirect coverage changes

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[MrAlias]

Please add a changelog entry.