🪞 Configure redundant repositories for Muzzle version discovery

[bric3]

What Does This Do

Add MUZZLE_MAVEN_REPOSITORY_PROXY as an optional preferred repository for Muzzle version discovery, retaining MAVEN_REPOSITORY_PROXY as a second route. No Depot endpoints are hard-coded; unset configuration preserves the existing behavior.

Motivation

Allow Muzzle to resolve metadata through another network route when one proxy endpoint is unavailable.

Additional Notes

Mirror of #12621 with configurable endpoints. Fabric remains opt-in until the CI environment provides DNS, routing, and JVM certificate trust. Aether queries both repositories and combines their versions, so a failed route can still delay resolution. CI with the variable unset does not validate Fabric connectivity.

Also this change requires the build image to have the necessary certicates.

Contributor Checklist

• Format the title according to the contribution guidelines
• Assign the type: and (comp: or inst:) labels in addition to any other useful labels
• Avoid using close, fix, or any linking keywords when referencing an issue
  Use solves instead, and assign the PR milestone to the issue
• Update the CODEOWNERS file on source file addition, migration, or deletion
• Update public documentation with any new configuration flags or behaviors
• Once approved, use merge queue to merge the PR

[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	14.83 s	14.75 s	[-0.3%; +1.4%] (no difference)
startup:insecure-bank:tracing:Agent	13.57 s	13.68 s	[-1.4%; -0.2%] (maybe better)
startup:petclinic:appsec:Agent	17.61 s	17.51 s	[-0.4%; +1.6%] (no difference)
startup:petclinic:iast:Agent	17.42 s	16.79 s	[-0.5%; +8.0%] (no difference)
startup:petclinic:profiling:Agent	17.44 s	17.22 s	[+0.1%; +2.4%] (maybe worse)
startup:petclinic:sca:Agent	17.60 s	17.56 s	[-0.6%; +1.1%] (no difference)
startup:petclinic:tracing:Agent	16.68 s	16.74 s	[-1.4%; +0.7%] (no difference)

Commit: 960b3b3d · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.