Disable mobile runtime runs for older branches

[LoopedBard3]

This disables the iOS and Android mobile runtime tests as part of the dotnet-runtime-perf pipeline for release branches. This will allow us to continue to get microbenchmark runs for the release branches without hitting issues due to new mobile configurations/updates.

Test runs:

• https://dev.azure.com/dnceng/internal/_build/results?buildId=2825877&view=results Demonstrates that this keeps mobile tests from running on release branch.
• https://dev.azure.com/dnceng/internal/_build/results?buildId=2825876&view=results Demonstrates that this still runs mobile tests when running on main.

[Copilot]

Pull Request Overview

This PR disables Mobile runtime performance tests for older release branches by adding a conditional check. The change prevents iOS Mono and NativeAOT scenario tests from running on branches that start with refs/heads/release.

Key Changes

• Added a conditional wrapper to exclude iOS performance tests from release branches

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[DrewScoggins]

LGTM

[LoopedBard3]

Errors are unrelated.