Fix super entity changer with location

[TheLimeGlass]

Description

• Adds INTERNAL change mode for the cases where the change mode gets applied again.
• Fixes modification of an entity' location not actually applying.
• Fixes ExprCoordinate's TriggerItem exiting a loop when a variable throws UnsupportedOperationException during conversion. (This currently still silently errors (not at the fault of the PR), this is bad. There are probably other parts of Skript that don't properly handle change, will address in a new issue)

Notes:

• Tests cannot be applied due to entity teleportation being a tick later.
• Local variables don't remember their source expression currently. Somewhere in the new conversion system, the source gets lost. This means the original issue of using a variable doesn't work, but using the raw expression last spawned wither will work now. Re-add local variable type hints #5457 adds a solution to this. Example is the source of the variable {_wither} should be the entity, but the source is always the converted Location.

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Target Minecraft Versions: any
Requirements: none
Related Issues: #6686