[Form] [Hackday] [2.7] Deprecate PRE_BIND, BIND and POST_BIND form events

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12648
| License       | MIT
| Doc PR        | none
please reverse var and const: `FormEvents::PRE_BIND === $eventName`