chore: default observability.enable_prometheus to true

[NicholasBlaskey]

Ticket

Description

Default observability.enable_prometheus to true for convenience. There was no reason it should have been defaulted to false since the performance is negligible.

Test Plan

Run a devcluster with no prometheus config and see that

det dev curl /debug/prom/metrics returns metrics

Run a devcluster with

        observability:
          enable_prometheus: false

det dev curl /debug/prom/metrics returns not found

Checklist

• Changes have been manually QA'd
• User-facing API changes need the "User-facing API Change" label.
• Release notes should be added as a separate file under docs/release-notes/.
  See Release Note for details.
• Licenses should be included for new code which was copied and/or modified from any external code.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.69%. Comparing base (9f6bbc9) to head (390c5d9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9222      +/-   ##
==========================================
- Coverage   44.70%   44.69%   -0.02%     
==========================================
  Files        1270     1270              
  Lines      155132   155136       +4     
  Branches     2437     2436       -1     
==========================================
- Hits        69351    69332      -19     
- Misses      85545    85568      +23     
  Partials      236      236              

Flag	Coverage Δ
backend	41.52% <100.00%> (-0.05%)	⬇️
harness	64.31% <ø> (ø)
web	35.23% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
master/internal/config/config.go	70.54% <100.00%> (+0.32%)	⬆️
master/test/testutils/fixtures.go	76.54% <100.00%> (+0.29%)	⬆️

... and 5 files with indirect coverage changes

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[kkunapuli]

I'm glad you updated the wording on what "enabled_prometheus" does. Prometheus endpoints are present makes a lot more sense!