[Crypto] C code sanitization

[tarakby]

• add C code sanitizers Makefile targets:
  • memory sanitizer msan (only works on Linux and with clang)
  • address sanitizer asan (only works on Linux)
  • other sanitizers (only work on Linux)
• add sanitizers (but msan) to a CI job and they are required to pass for new PRs
• msan has many false positive errors from use-of-unitialized-value. These errors have been debugged one by one to make sure no uninitialized memory has been read.
• NO_MSAN macro has been added during debugging to disable msan in functions. The macro was left in the code for future debugging. It is only defined when compiling with defined MSAN (look at the c-msan target in Makefile).

Side changes:

• Update ./bls_src/README with instructions of updating BLST version.
• clean up non used Fermat modular inversion and Montgomery modular expo.
• minor optimization to Fr_is_zero.
• update DEBUG macro .

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -7.54% ⚠️

Comparison is base (20b89d2) 61.23% compared to head (8314b0c) 53.70%.

Additional details and impacted files

@@                      Coverage Diff                      @@
##           feature/blst-based-crypto    #4654      +/-   ##
=============================================================
- Coverage                      61.23%   53.70%   -7.54%     
=============================================================
  Files                            280      857     +577     
  Lines                          28651    79948   +51297     
=============================================================
+ Hits                           17545    42937   +25392     
- Misses                          9653    33615   +23962     
- Partials                        1453     3396    +1943     

Flag	Coverage Δ
unittests	53.70% <ø> (-7.54%)	⬇️

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see 580 files with indirect coverage changes

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