Provides an arm backend for matrix multiplies using google/ruy and math
functions through simde (https://simd-everywhere.github.io/blog/about/)
effectively getting marian-decoder to run on ARM.

The following cmake flags are added:

- USE_INTGEMM (to switch intgemm on/off)
- USE_RUY (to switch ruy on/off)
- USE_ONNX_SGEMM (use onnx sgemm added by wasm to provide attention
  matrix multiply which is currently reliant on a BLAS library).
- USE_SIMDE (swaps out existing intel based functions by using SIMDE
  instead).

The built marian-decoder is tested on an Oracle Cloud ARM Machine with
the following specs:

  Architecture   : aarch64
  CPU op-mode(s) : 32-bit, 64-bit
  Byte Order     : Little Endian
  Vendor ID      : ARM
  Model name     : Neoverse-N1
  Flags          : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp
                   asimdhp cpuid asimdrdm lrcpc dcpop asimddp ssbs

A CI check on GitHub actions is added to use android-ndk cross-compile
targetting arm64-v8a. The built binary is tested to work on an Android
Phone using termux (Samsung M30s).

Successful android build additionally requires a patch (sentencepiece ->
protobuf). See opencv/opencv#17282 and
opencv/opencv#19049.

-Werror etc causes issues with ruy (-Wmulti-line-comment) and are
disabled.

The following minor changes are also applied:

 - Remove M32_BINARIES use COMPILE_WASM for -m32
 - Hide msse4.1 if unknown platform
 - faiss was previously hardcoded for platforms with SSE available. This
   has been mitigated by adding a refernce standard cpp implementation of
   the missing function.
 - Exclude packed_gemm_....cpp from sources if USE_FBGEMM=off
 - MSVC workaround following
   browsermt#56 (comment)