[saffron] integration test

[martyall]

This PR tries to document all the user flow features we have in a single test: upload/update/read-proof/storage-proof. The CLI has not kept up with these flows, but hopefully this test can serve as docs for whatever comes next.

This test is in tests/integration.rs/. All other changes are small borrow/move refactors that came up naturally while trying to write it.

[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.

Project coverage is 77.07%. Comparing base (304b505) to head (fd1dcd7).

Files with missing lines	Patch %	Lines
saffron/src/main.rs	0.00%	2 Missing ⚠️
saffron/src/query.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##           martin/saffron-read-pf    #3039      +/-   ##
==========================================================
- Coverage                   77.07%   77.07%   -0.01%     
==========================================================
  Files                         264      264              
  Lines                       62348    62349       +1     
==========================================================
- Hits                        48056    48053       -3     
- Misses                      14292    14296       +4     

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