refacto: cleanup state traits, CachedState interior mutability

[tdelabro]

In this PR:

• StateReader doesn't require a mutable reference to self anymore
• therefore, CachedState uses a Cell to have interior mutability for it's cache
• All state traits arguments are given by value, not ref, as they all impl Copy
• All state traits methods return a StateResult as we don't know for sure all impl will be infallible
• The method to compute state diff is taken out of the state traits, and into impl CachedState

This change is 

[codecov-commenter]

Codecov Report

Attention: 93 lines in your changes are missing coverage. Please review.

Comparison is base (44832c1) 70.97% compared to head (9c11469) 70.65%.

Files	Patch %	Lines
crates/blockifier/src/state/cached_state.rs	69.42%	81 Missing and 4 partials ⚠️
...ve_blockifier/src/state_readers/py_state_reader.rs	0.00%	5 Missing ⚠️
...tive_blockifier/src/state_readers/papyrus_state.rs	60.00%	2 Missing ⚠️
...tes/blockifier/src/test_utils/dict_state_reader.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1232      +/-   ##
==========================================
- Coverage   70.97%   70.65%   -0.32%     
==========================================
  Files          59       59              
  Lines        7341     7473     +132     
  Branches     7341     7473     +132     
==========================================
+ Hits         5210     5280      +70     
- Misses       1717     1782      +65     
+ Partials      414      411       -3     

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[tdelabro]

superseded by #1325