Update Style Guidelines

[ryley-o]

Description of the change

Refactor and update style guidelines to reflect preference to not use Solidity modifiers.

This partially completes #483

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[jakerockland]

This is fantastic – thank you @ryley-o

One note, lets wait to fully close #483 until we've also done the cleanup of usage of existing modifiers (can also split the issue into two if you'd prefer).

[ryley-o]

sounds good - the remaining work of removing modifiers from all active contracts has been tagged as a polish week task 🙏 thanks for calling that out!