Mark RuleWalker, ProgramAwareRuleWalker, and ScopeAwareRuleWalker as deprecated

[JoshuaKGoldberg]

Recapping #2522: RuleWalker-based rules are slow, so it's generally preferable to use applyWithFunction instead of applyWithWalker.

if folks shouldn't use RuleWalker, it would be good to actively encourage new PRs not to. TSLint could mark them as @deprecated in their doc comments and put // tslint:disable-next-line:deprecation with links to issue(s) tracking converting them to walk functions.

Edit: TwoThree thumbs up from over a month - marking as accepting PRs 😊

[adidahiya]

let's do this for 5.13.0. also need to update the relevant docs in docs/develop/custom-rules/index.md