Unnecessary `$$invalidate` calls during component creation

[mrkishi]

There's no need to instrument assignments with calls to $$invalidate inside the main instance() function body as all variables are initially set to dirty already.

It wouldn't be a huge improvement, but it's unnecessary work nonetheless.

[mrkishi]

A straight ahead tweak on the current ast walk comes upon two complications: labelled statements and store reassignments. They need to be instrumented regardless of being in the main control flow or not.

[mrkishi]

PR incoming