Transform $ReadOnly to Readonly 37/n (#55066)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55066

We are transforming the following utility types to be more consistent with typescript and better AI integration:

* `$NonMaybeType` -> `NonNullable`
* `$ReadOnly` -> `Readonly`
* `$ReadOnlyArray` -> `ReadonlyArray`
* `$ReadOnlyMap` -> `ReadonlyMap`
* `$ReadOnlySet` -> `ReadonlySet`
* `$Keys` -> `keyof`
* `$Values` -> `Values`
* `mixed` -> `unknown`

See details in https://fb.workplace.com/groups/flowlang/permalink/1837907750148213/.

drop-conflicts

Command:

`js1 flow-runner codemod flow/transformUtilityType --legacy-type='$ReadOnly'`

Changelog:[internal]

Differential Revision: D90146145

fbshipit-source-id: 4b71784a36f8286f3be620969ea408cf8a0aac80