Add Apple M1 support

[nbigaouette]

This PR adds Apple M1 support.

Note that no pre-built microsoft/onnxruntime binaries exists for the M1 (aarch64) so it needs to be manually compiled (see ONNX_Compilation_Notes.md for some notes on that). This means one has to use ORT_STRATEGY=system and ORT_LIB_LOCATION=/path/to/onnxruntime (see README.md).

Their is no CI for this arch so it will not be tested. See actions/runner-images#2187 for GitHub Actions' M1 support request.

[codecov-io]

Codecov Report

Merging #74 (a5e7f95) into master (1948683) will increase coverage by 1.53%.
The diff coverage is 75.71%.

@@            Coverage Diff             @@
##           master      #74      +/-   ##
==========================================
+ Coverage   14.58%   16.11%   +1.53%     
==========================================
  Files          18       19       +1     
  Lines         960     1117     +157     
==========================================
+ Hits          140      180      +40     
- Misses        820      937     +117     

Impacted Files	Coverage Δ
...untime-sys/src/generated/macos/aarch64/bindings.rs	0.00% <ø> (ø)
onnxruntime/src/session.rs	0.00% <0.00%> (ø)
onnxruntime/src/tensor/ort_tensor.rs	79.16% <75.47%> (-3.19%)	⬇️
onnxruntime/src/lib.rs	42.55% <84.61%> (+5.20%)	⬆️
onnxruntime/src/error.rs	62.50% <100.00%> (+5.35%)	⬆️

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