Bytecode size improvements

[kyriediculous]

What does this pull request do? Explain your changes. (required) Improves the bytecode size of our contracts by making some optimizations, prevents running into the 24kb contract limit in the future

Specific updates (required)

• Moved onlyGov modifier body into an internal function to prevent inlining modifier code everywhere
• Mark governance parameter updates with an enum instead of hardcoded strings

How did you test each of these updates (required)

Does this pull request close any open issues?

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