fix(reports) skip mesh when namespace-limited

[rainest]

What this PR does / why we need it:

Disable mesh detection if the configuration uses --watch-namespaces. The mesh detector attempts to scan all namespaces and cannot be configured to use the multi-namespace cache used by the manager. Since it will fail when --watch-namespaces is set, disable it altogether.

Which issue this PR fixes:

Fix #3158

Special notes for your reviewer:

Disabling altogether since the report data isn't critical. Alternatives are:

• Find some way to use the manager client for mesh detection. I don't think this is easily doable without taking it out of the reports system and instead building it into the Service controller. controller-runtime does not expose the manager client and I don't particularly want to roll my own MNCB/Kubernetes API client integration just for this.
• Only scan the controller namespace. We should always have access to this, but it's not guaranteed to have a mesh enabled if there is one.

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[codecov]

Codecov Report

Base: 74.0% // Head: 74.1% // Increases project coverage by +0.1% 🎉

Coverage data is based on head (e44612e) compared to base (9bce9e3).
Patch coverage: 0.0% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3336     +/-   ##
=======================================
+ Coverage   74.0%   74.1%   +0.1%     
=======================================
  Files        110     110             
  Lines      13263   13268      +5     
=======================================
+ Hits        9822    9842     +20     
+ Misses      2808    2798     -10     
+ Partials     633     628      -5     

Impacted Files	Coverage Δ
internal/manager/run.go	47.6% <0.0%> (-1.2%)	⬇️
internal/manager/utils/reports.go	0.0% <0.0%> (ø)
...nternal/controllers/gateway/udproute_controller.go	73.6% <0.0%> (-2.8%)	⬇️
internal/dataplane/kongstate/service.go	66.0% <0.0%> (-1.3%)	⬇️
internal/dataplane/parser/parser.go	91.3% <0.0%> (+1.6%)	⬆️
...nternal/controllers/gateway/tcproute_controller.go	75.6% <0.0%> (+2.6%)	⬆️
...ternal/controllers/gateway/httproute_controller.go	55.8% <0.0%> (+3.3%)	⬆️

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