Add value equality for TLS configurations and trust stores

[samuel-williams-shopify]

Equivalent TLS configurations currently compare by object identity, forcing connection caches to serialize and digest them to share clients by value. Add ==, eql?, and hash to TLS::Configuration and TLS::TrustStore so they can be used directly as cache keys.

Equality includes the exact PEM strings, certificate order, trust store system-certificate policy, and configuration verification policy. equal? retains its object-identity semantics. Freezing either object copies and freezes its nested certificate data, so a cache can retain an immutable snapshot without freezing the caller's configuration or its inputs:

configuration = tls_configuration&.dup&.freeze
key = [url, configuration]

This supports removing Marshal serialization and SHA-256 cache keys from async-grpc-compatible #10. Existing redacted inspect output keeps certificate and private-key material out of cache inspection.

Validation on Ruby 4.0.7:

• io-endpoint: 121 tests, 260 assertions; both changed TLS classes have 100% line coverage.
• PR Fix SSLServer#accept failures causing accept loop to exit. #10 with the direct configuration key and this io-endpoint branch: 116 tests, 390 assertions, 100% line coverage, including connection reuse, mutation isolation, and private-key redaction.
• RuboCop passes in both repositories; io-endpoint API documentation coverage is 145/145.