Bundle the per-rule configurations/overrides

[jacobotb]

What problem are you trying to solve?

We have per-rule enable/disable, per-rule arguments, and per-rule severity/category overrides, all spread across three different objects that are initialized separately, passed separately, and used separately.

We will be adding more.

What is your solution?

This PR bundles those objects together so only one object needs to be initialized, and only one object needs to be passed to the 'analyze' function.

Since the analyze function takes one file name and a list of rules, we can avoid parsing the filename more than once. To that end, the RuleConfigProvider has a config_for_file function that generates a RuleConfig scoped to a particular file, with the file name all parsed up nicely. This is the object that is passed to the analyze function.

The RuleConfig then has functions to get argument values, severity, enable/disable status, etc., for any rule and for the file it was created for.

Alternatives considered

What the reviewer should know