[Analyzer][StreamChecker] Adding PreCall and refactoring (NFC).

Summary:
Adding PreCall callback.
Argument validity checks are moved into the PreCall callback.
Code is restructured, functions renamed.
There are "pre" and "eval" functions for the file operations.
And additional state check (validate) functions.

Reviewers: Szelethus

Reviewed By: Szelethus

Subscribers: xazax.hun, baloghadamsoftware, szepet, a.sidorin, mikhail.ramalho, Szelethus, donat.nagy, dkrupp, gamesh411, Charusso, martong, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75612