fix($compile): fix missing error handling when new-scope directive is applied before isolated-scope directive

[buunguyen]

Given dirA, which requests new scope, and dirB, which requests new & isolated scope. If dirA is applied after dirB, $compile reports an error ('Multiple directives [dirB, dirA] asking for new/isolated scope'), which is expected. However, if dirA is applied before dirB, e.g. because dirA has higher priority, then no error is thrown and dirA shares the isolated scope created for dirB. This is inconsistent and can break dirA, which might need to access to parent scope's members. This fix addresses this situation by throwing error regardless of order of directive application.

Closes #4402

[mary-poppins]

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[petebacondarwin]

Moving to 1.2.5 for further discussion:
I am not sure if this counts as a breaking change since it could well break applications that currently naively do have directives that "sort of" work right now and would break with an exception after this commit.

[caitp]

I mention this in 1307, but I realized that it seems to be a different issue, not throwing when two directives on the same element create a new (not isolate) scope. (this is after changing their plnkr to use 1.2.3).

So this might be a different issue, I'm not sure. In any case it seems like it's probably not desirable

[petebacondarwin]

We can now land this since 1.3 can have breaking changes.