Refactor $parse

[IgorMinar]

We need to make a major cleanup in $parse as it contains a lot of legacy code that is not needed.

The work should be broken down into 3 PRs so that it's easier to review:

1/ remove support for JSON parsing (this is a feature that is not exposed via public api and the code just sits there for no good reason)
2/ remove support for promise unwrapping (this a deprecated feature, which we want to remove in 1.3)
3/ benchmark the impact of removing function generation (via new Function) and only to our simpleGetterFn implementation. This needs to be done across browsers - mainly IE9, IE 11, latest Firefox, latest Chrome, mobile Chrome and mobile Safari. Depending on the results, we should remove or keep this code path.

[rodyhaddad]

1/ and 2/ are taken care of by #7552 and #7555

For 3/, running these two benchmarks {new Function, simple getters}, and extracting the numbers to this doc, the difference between the two across browsers doesn't seem that significant, and so no action will be taken for now.

[lgalfaso]

@rodyhaddad I do not understand the reasoning, if the numbers are about the same, then we should remove the new Function path and simplify the code