Fix multi-statements in nested triggers

[jycor]

changes:

• have different savepoint names
  • this fixes nested triggers overwriting save points and clearing the same savepoint
• handle aliases independently for each statement in trigger blocks
• sync up prepend and scope nesting for triggers
• wrap applyTrigger rule wraps triggerExecutors over individual statements in BeginEndBlocks
  • this prevents wrapping triggerExecutors over the wrong statements (not matching event or table)

related: https://github.com/dolthub/dolt/issues/8213