Deprecate the x86-64-modern arch

Deprecate the x86-64-modern arch

Explicitly describe the architecture as deprecated,
it remains available as its current alias x86-64-sse41-popcnt

CPUs that support just this instruction set are now years old,
any few years old Intel or AMD CPU supports x86-64-avx2. However,
naming things 'modern' doesn't age well, so instead use explicit names.

Adjust CI accordingly. Wiki, fishtest, downloader done as well.

closes https://github.com/official-stockfish/Stockfish/pull/4691

No functional change.