Update x265 Portfiles and x265 port to compile in the NEON patch for Apple Silicon

[janngobble]

x265 compiles for Apple Silicon but there is a x265 patch for enabling the fast NEON intrinsics.

At the following URL, it says: "The FFmpeg file for Apple Silicon includes the x265 NEON patch. This makes the encoding speed of x265 much faster. "

​https://ffmpegfromzerotohero.com/blog/

Can we enable this on the FFMPEG/X265 port MacPorts uses?

ps: x265's Neon ASM is all in gas format so might work if compiled with gcc, doesn't work with clang, nasm doesn't get used for the arm ASM and doesn't work if you force it to use nasm.