RequireUtils 'self' uses address(this) instead of msg.sender

[ScreamingHawk]

This change helps enforce the default context retention for the intent address by expecting delegate calls when making xxxSelf requests.

I'm impartial on this one. From a gas and complexity standpoint I think keeping msg.sender is the right approach Maybe the terminology self should be updated to sender to be less ambiguous?

A cleaner approach would be to remove all the xxxSelf functions and expect calls to populate msg.sender/address(this) using hydrate logic. This would be even more gas inefficient.

[Agusx1211]

I don't think it is worth doing this change at this stage, even a name change seems unnecessary since we have been using this naming schema for a long time and it hasn't caused confusion so far. We can change it in v2.