Io.netty/netty-codec-http: netty rtspdecoder method-token smuggling via trailing control byte

### Summary `RtspMethods.valueOf()` silently strips trailing control bytes (any character with code point <= 0x20, the full range that `String.trim()` removes) before performing a cache lookup against its ten pre-populated method constants. A wire-delivered RTSP request whose method token ends with a trailing control byte — for example `PLAY\x00` or `PLAY\r`, immediately before the separating space — is decoded by `RtspDecoder` as a fully successful PLAY request, with `decoderResult().isSuccess() == true and request.method() == RtspMethods.PLAY` (same object reference as the cached singleton). The application layer cannot distinguish this from a clean `PLAY` request. This is the same root cause as #16723 and #16971, in a sibling that those fixes did not reach. The fix for `HttpMethod` hardened `HttpMethod.valueOf()` directly, but `RtspMethods.valueOf()` has its own independent `checkNonEmptyAfterTrim()` call that runs before the cache lookup — meaning a trailing-control-byte token hits the cache before the hardened `HttpMethod` constructor ever sees it. ### Reproduction Minimal wire-level reproduction Send the following raw bytes to any Netty-based RTSP server using R

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