[De-Angular] Clean angular context in Data plugin

[ananzh]

• Rename/Remove toAngularJSON(filter.input.query))
  This toAngularJSON function is a utility to convert an object into its JSON representation. The naming toAngularJSON might suggest that it was used by some Angular code, but from the provided implementation, it looks like a wrapper around the standard JSON.stringify method. Currently we completely removed AngularJS, therefore the simplest way to resolve is to just rename the method. The best way would be checking whether we could simply use JSON.stringify to replace this function.
• Remove src/plugins/data/common/search/aggs/utils/to_angular_json.ts and clean src/plugins/data/common/search/aggs/utils/index.ts.

[ashwin-pc]

Marked the function as deprecated, it will be removed in 3.0

[ShatilKhan]

Hey can I work on this?
it would be great to have some more info

[wbeckler]

@ShatilKhan I believe the remaining work here is to remove references to angular while still getting tests to pass.

[ShatilKhan]

I'm on it

[ShatilKhan]

In the 1st part of the issue @ananzh stated
Update toAngularJSON(filter.input.query))
to toAngularJSON(filter.input.query)) in..
They are the same thing, so I was a bit confused, can you please tell me the correct replacement?

[ShatilKhan]

PR is up
I've made one change only, a bit confused about the other changes requested
will try to discuss this in today's office hour