Build perf: Enable ReadyToRun for managed interop assembly

[MariusStorhaug]

Summary

Evaluate and enable ReadyToRun publishing for the managed interop assembly to reduce first-call JIT costs.

Why

R2R can improve startup/cold-path latency for frequently imported modules with small managed wrappers.

Proposed change

• Update project build settings to enable ReadyToRun for relevant targets.
• Validate package size impact and runtime compatibility across supported RIDs.
• Ensure CI publishes and tests artifacts with this mode.

Acceptance criteria

• Cold-start benchmark shows improvement or no regression.
• No functional regressions across supported platforms.
• Package size impact is documented and acceptable.
• CI/build pipeline remains green.