qmlsc: Implement Temporal Dead Zone (TDZ) checks

Currently, JS functions that have multiple levels of scopes – and variables that are accessed across scopes – will likely be uncompilable.

Code

import QtQuick

Window {
    width: 640
    height: 480
    visible: true

    function foo(): void {
        let v1 = 1
        let v2 = 2

        if (true) {
            v1 = v2
        }
    }
}

Compiler output

Warning: Main.qml:13:4: Could not compile function foo: Instruction "generate_DeadTemporalZoneCheck" not implemented [compiler]
			v1 = v2
			^^

Partial workaround
For simple cases like the example above, removing the curly brackets around v1=v2 would do the trick