feat(retry): update backoff to v5, fix the breaking changes in that version

[yumosx]

• Remove unsupported fields in v5: MaxElapsedTime, Stop and Clock
• Use time.Now() and time.Since() to manually track elapsed time

Fix #6417

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.8%. Comparing base (2b4e1a3) to head (ede8f90).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #6419     +/-   ##
=======================================
- Coverage   81.8%   81.8%   -0.1%     
=======================================
  Files        283     283             
  Lines      24928   24910     -18     
=======================================
- Hits       20401   20386     -15     
+ Misses      4122    4119      -3     
  Partials     405     405             

see 8 files with indirect coverage changes

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[dmathieu]

This code is auto-generated from the templates here:
https://github.com/open-telemetry/opentelemetry-go/tree/main/internal/shared/otlp/retry

They need to be updated, and make generate needs to be run locally.