require-meta-schema: Add requireSchemaPropertyWhenOptionless option

[bmish]

Add requireSchemaPropertyWhenOptionless option to require-meta-schema rule (default true initially to match current behavior, could be changed in major release).

Why?

• Some people don't want to bother including schema: [] when their rules have no options (example)
• schema: [] might not be necessary in the future if the ESLint default behavior changes (see below)

I have an update to share regarding the require-meta-schema rule. I have recommended to the ESLint team that schemas should be required for rules with options and they are interested in this idea so I'll be opening an RFC for it targeting ESLint 9.

With this change, rules without options will no longer need to specify schema: [], as that will be the default behavior. That means we can update the require-meta-schema rule to only require the schema property for rules that actually have options (which is the same as how require-meta-fixable only requires the fixable property for rules with fixers).

As a result of this change, we should be able to enable the require-meta-schema rule as recommended in eslint-plugin-eslint-plugin v4.

Originally posted by @bmish in #120 (comment)