alias function definitions to variables so terser can mangle their names

[samualtnorman]

like as in turn

let someFunctionWithALongName = () => {
	// do some stuff
}

someFunctionWithALongName()
someFunctionWithALongName()

into

let someFunctionWithALongName = () => {
	// do some stuff
}

let _00000000000_LOCAL_FUNCTION_ALIAS_someFunctionWithALongName_ = someFunctionWithALongName

_00000000000_LOCAL_FUNCTION_ALIAS_someFunctionWithALongName_()
_00000000000_LOCAL_FUNCTION_ALIAS_someFunctionWithALongName_()

and then hand it off to terser.

terser currently has a bug that will cause the name of someFunctionWithALongName() to be clobbered if I do the above transformation.
I will wait for terser to amend this.