function-name rule - add support for linting protected methods

[netroy]

this adds support for protected class methods on classes for the function-name rule.

also, removed the duplicate regexp across public, private & protected methods.

[msftclas]

Hi @netroy, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

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[msftclas]

@netroy, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, MSBOT;

[HamletDRC]

Thanks! I updated the readme as well.