Burst pylint.checkers base into multiple file

[Pierre-Sassoulas]

Type of Changes

	Type
✓	🔨 Refactoring

Description

pylint.checker.base was 2600 lines long which was impacting analysis performance in IDE (more than 4s to get a new analysis after a save in Pycharm). This also permitted to find unused code and to remove it.

[coveralls]

Pull Request Test Coverage Report for Build 2036694117

• 1130 of 1152 (98.09%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.07%) to 94.167%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pylint/checkers/base/name_checker/checker.py	248	250	99.2%
pylint/checkers/base/docstring_checker.py	85	88	96.59%
pylint/checkers/base/basic_checker.py	372	379	98.15%
pylint/checkers/base/basic_error_checker.py	211	221	95.48%

Totals
Change from base Build 2036452518:	0.07%
Covered Lines:	15289
Relevant Lines:	16236

---

💛 - Coveralls

[cdce8p]

We should do #5221 first. I still need to look at that though.