Add verify-storage-proof command to cli and e2e

[martyall]

Summary

Second part of #2985 -- added the verify-storage-proof command to the cli and to the e2e script, completing the e2e user flow for

• upload data to SP
• request proof of storage from SP
• verify proof of storage

Changes

• Added verify-storage-proof command to cli and e2e script.
• store the alpha and folded_commitment values on the blob struct. 9ff0ae7
• use the folded_commitment as the sanity-check between the user/verifyer and storage provider. There has been some back and forth on this (see here and here), but it greatly simplifies things to do this and its cheap. see this diff for details

[codecov]

Codecov Report

Attention: Patch coverage is 13.33333% with 52 lines in your changes missing coverage. Please review.

Project coverage is 77.05%. Comparing base (bd4a885) to head (40d56e7).
Report is 26 commits behind head on master.

Files with missing lines	Patch %	Lines
saffron/src/main.rs	0.00%	34 Missing ⚠️
saffron/src/commitment.rs	0.00%	14 Missing ⚠️
saffron/src/cli.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2979      +/-   ##
==========================================
+ Coverage   76.93%   77.05%   +0.12%     
==========================================
  Files         262      260       -2     
  Lines       61614    61445     -169     
==========================================
- Hits        47401    47345      -56     
+ Misses      14213    14100     -113     

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