chore: Address otel review feedback

[alexandear]

• Use example/go.mod instead of example/otel/go.mod for consistency with other examples.
• Upgrade to the latest go.opentelemetry.io packages.
• Add dependabot config for otel directory.
• Change to raw strings instead of constants for consistency in tests.

Follows #3938

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.50%. Comparing base (5d70283) to head (7fe9be0).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3969   +/-   ##
=======================================
  Coverage   93.50%   93.50%           
=======================================
  Files         206      206           
  Lines       17550    17550           
=======================================
  Hits        16411    16411           
  Misses        938      938           
  Partials      201      201           

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[gmlewis]

Thank you, @alexandear!
LGTM.
Merging.