dev: remove outside_execution checks & docs

[enitrat]

execute_from_outside purpose is that validate and execute are limited in functionalities. We could not run all EVM checks in validate , and our move to a "real" Starknet chain required a solution to handle the underlying starknet transaction fee for our users.

Thus, we needed to implement a paymaster functionality.
All EVM tx rules validation are now handled in the execute part of a transaction to bypass the limitations of validate , and both these entrypoints have been disabled.
We use a fleet of relayer accounts to sponsor the Starknet cost of the transaction for our users, so that they don't have to worry about Starknet gas
For this, we implemented the execute_from_outside entrypoint as defined in SNIP-9

The outside_execution nonce is not signed, thus anyone can send a transaction to this entrypoint with any value for outside_execution and pass the first checks: it's indeed useless
However, there should not be a security risk: the EVM transaction sent

    calldata_len: felt,
    calldata: felt*,
    signature_len: felt,
    signature: felt*,

is signed by the EOA owner, and cannot be replayed

In the end: any checks on outside_execution is useless.

Time spent on this PR:

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Resolves #

What is the new behavior?

• Remove checks from the Outside execution
• Add some docs

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This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.9%. Comparing base (73356ca) to head (ea300cb).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1437     +/-   ##
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- Coverage   62.9%   62.9%   -0.1%     
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  Files         49      49             
  Lines       8393    8386      -7     
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- Hits        5282    5275      -7     
  Misses      3111    3111             

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	62.9% <ø> (-0.1%)	⬇️

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