Create a pre call hook for execTransaction

[akshay-ap]

EDIT: Earlier it was proposed to create post hook function. But, later we realised issues:

• changes the order of the emitted events
• compiler reports stack too deep error

Updated Expected outcome

• A pre-hook which is called before execution of call using execTransaction with given parameters is performed

So, we decided to create pre-hook rather that post-hook.

Context

#772 added a post call hook onAfterExecTransactionFromModule for execTransactionFromModule* methods. This helped to remove the overriding execTransactionFromModule function in SafeL2 which was earlier needed so that event SafeModuleTransaction gets emitted and then called parent implementation.

With #772, overriding onAfterExecTransactionFromModule and emitting the event SafeModuleTransaction does the work.

Similarly, SafeL2 also overrides execTransaction to emit the event SafeModuleTransaction. This issue aims at introducing a similar post hook method namely onAfterExecTransaction which removes the requirement for overriding execTransaction in SafeL2.

Expected outcome

- A post hook function similar to onAfterExecTransactionFromModule