fix: allow ref self until sozo can handle starknet contracts

[glihm]

We've disabled the use of ref self into dojo contracts.
However, library like origami was intensively using it. And due to the current situation where sozo can't manage starknet contract (which may require some time), this PR ensures that advanced users can use ref self.

ref self is actually mostly used to ensure functions like emit from starknet plugin can be used. And not to directly modify the system storage on its own.

It is important to consider that dojo systems are meant to be stateless.

[codecov]

Codecov Report

Attention: Patch coverage is 91.30435% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 69.65%. Comparing base (a573198) to head (373320f).
Report is 16 commits behind head on main.

Files	Patch %	Lines
crates/dojo-lang/src/contract.rs	91.30%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1879      +/-   ##
==========================================
- Coverage   70.29%   69.65%   -0.64%     
==========================================
  Files         313      315       +2     
  Lines       35769    36014     +245     
==========================================
- Hits        25143    25085      -58     
- Misses      10626    10929     +303     

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