tpm2_hash: Change default hashing alg from sha1 to sha256

[idesai]

Fixes #3340

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 74.30%. Comparing base (1fdb01a) to head (58d0129). Report is 33 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3342      +/-   ##
==========================================
- Coverage   74.38%   74.30%   -0.09%     
==========================================
  Files         173      173              
  Lines       23673    23754      +81     
==========================================
+ Hits        17610    17651      +41     
- Misses       6063     6103      +40     

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