Cleans some utils

[Efnilite]

Description

Cleans up some util classes. This is to reduce the amount of code we have to maintain, while also reducing the use of archaic self-written replacements for common Java equivalents.

• Classes marked as deprecated for removal:
  • ReversedListView -> Wasn't used.
  • CyclicList -> Wasn't used.
  • BidiMap -> Can be replaced with BiMap. Wasn't used.
  • BidiHashMap -> Can be replaced with BiMap. Wasn't used.
  • Validate -> Can be replaced with Preconditions. The few uses of this class have been changed to use Preconditions.
  • Setter -> Can be replaced with Consumer. Had several uses, but all have been replaced with Consumer. This is not a breaking change as these are functionally equivalent for the user.
  • Predicate -> Can be replaced with Java's Predicate. Wasn't used.
  • CaseInsensitiveString -> Can be replaced with usage of equalsIgnoreCase. Wasn't used.
• Classes removed
  • Old Slot (ch.njol.skript.util.Slot) -> Has been deprecated since 2018. Wasn't used.
  • SoundUtils -> Wasn't used.

---

Target Minecraft Versions: any
Requirements: none
Related Issues: none

[Moderocky]

Some of these are duplicated in #6670