fix($compile): fix memory leak

[lgalfaso]

For functions that have a '&' binding on the scope, change the function from an inline definition to an external definition so the function closure has no access to the parent scope.

Closes #6794

Note: I am not sure this if this is a Chrome GC bug (as the function never uses the parent scope), but for the scenario from the issue, the patch fixes the leak

[mary-poppins]

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• Uses the issue template (#6801)

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Thanks again for your help!

[lgalfaso]

Attached is a Chrome heap snapshot after clicking on "home", then "leak", then "home". It shows the reference to the function (in fact, the entire scope was not GCed)

I still think this is a Chrome bug.

As a side note, I was not able to make it leak more than one scope

[IgorMinar]

as discussed with @lgalfaso today there is no evidence that this patch actually does anything. applying it or not, the leak is still present. the leak that we can reproduce is present even when & bindings are not being used.

[lgalfaso]

Reopening for visibility