Add benchmarks

[Taowyoo]

This PR closes #8 .

[codecov]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (003f727) 91.94% compared to head (8e13927) 92.37%.

Files	Patch %	Lines
rustls-mbedcrypto-provider/src/tls12.rs	66.66%	4 Missing ⚠️
rustls-mbedcrypto-provider/src/error.rs	0.00%	2 Missing ⚠️
rustls-mbedcrypto-provider/src/hmac.rs	88.23%	2 Missing ⚠️
rustls-mbedcrypto-provider/src/tls13.rs	66.66%	2 Missing ⚠️
rustls-mbedcrypto-provider/src/kx.rs	97.22%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #16      +/-   ##
==========================================
+ Coverage   91.94%   92.37%   +0.42%     
==========================================
  Files          16       16              
  Lines        1812     1796      -16     
==========================================
- Hits         1666     1659       -7     
+ Misses        146      137       -9     

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[s-arash]

So we are about 10-20 times slower than ring in crypto operations? 🤔
Is it because mbedtls is slow?

[Taowyoo]

So we are about 10-20 times slower than ring in crypto operations? 🤔 Is it because mbedtls is slow?

@s-arash Yes, mainly because mbedtls is slow.