Commit Message: Reflection-based deterministic message hashing
Additional Description: Comparing config used to be done with "deterministic" serialization and a hash of that, but it turned out deterministic serialization was not in fact deterministic enough (Any messages could contain reordered maps or even other fields). The recommendation in protobuf docs is "if you want a deterministic order do it yourself". (Note that the linked comment also suggests that SetSerializationDeterministic should work for our purposes here, but protocolbuffers/protobuf#5731 is the relevant unaddressed bug about Any fields.)

The prior method of achieving determinism by expanding Any via TextFormat serialization is slow enough that it shows up on performance graphs as a significant cost (about 1/4 of our total startup time).

This change is quite a lot of code, but should give us a deterministic hash with a much faster runtime than transforming to and then hashing a human-readable string.

Risk Level: Some; if it's broken it might cause config updates to not apply, or cache entries to collide.
Testing: Many unit tests, and a bit extra in the existing hash test. Benchmark results from bazel run -c opt test/common/protobuf:utility_speed_test:

-----------------------------------------------------------------------------------
Benchmark                                         Time             CPU   Iterations
-----------------------------------------------------------------------------------
bmHashByDeterministicHash/map                 35663 ns        35662 ns        20288
bmHashByTextFormat/map                       376608 ns       376503 ns         1892
bmHashByDeterministicHash/recursion           13682 ns        13681 ns        51381
bmHashByTextFormat/recursion                  30239 ns        30239 ns        23463
bmHashByDeterministicHash/repeatedFields      21024 ns        21023 ns        33263
bmHashByTextFormat/repeatedFields            150444 ns       150443 ns         4645

Docs Changes: n/a
Release Notes: n/a
Platform Specific Features: n/a
Runtime Guard: envoy.restart_features.use_fast_protobuf_hash

Request variables

Key	Value
ref	279f0dabf74f1aa71574c38e0924961e368ae9ad
sha	fbed541
pr	30761
base-sha	afdc660
actor	@ravenblackx
message	Reflection-based deterministic message hashing...
started	1702396314.098278
target-branch	main
trusted	false

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