proxy: v2.86.0

[olix0r]

This release includes the results from continued profiling & performance
analysis. In addition to modifying internals to prevent unwarranted
memory growth, we've introduced new metrics to aid in debugging and
diagnostics: a new request_errors_total metric exposes the number of
requests that receive synthesized responses due to proxy errors; and a
suite of stack_* metrics expose proxy internals that can help us
identify unexpected behavior.

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• trace: update tracing-subscriber dependency to 0.2.1 (trace: update tracing-subscriber dependency to 0.2.1 linkerd2-proxy#426)
• Reimplement the Lock middleware with tokio::sync (Reimplement the Lock middleware with tokio::sync linkerd2-proxy#427)
• Add the request_errors_total metric (Record a metric of proxy errors linkerd2-proxy#417)
• Expose the number of service instances in the proxy (Expose the number of service instances in the proxy linkerd2-proxy#428)
• concurrency-limit: Share a limit across Services (concurrency-limit: Share a limit across Services linkerd2-proxy#429)
• profiling: add benchmark and profiling scripts (profiling: add benchmark and profiling scripts linkerd2-proxy#406)
• http-box: Box HTTP payloads via middleware (http-box: Box HTTP payloads via middleware linkerd2-proxy#430)
• lock: Generalize to protect a guarded value (lock: Generalize to protect a guarded value linkerd2-proxy#431)