Add Consider-using-f-string checker

[DanielNoord]

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Type of Changes

	Type
✓	✨ New feature

Description

Add consider-using-f-string checker
This adds a checker for normal strings which are formatted
with .format() or '%'.
The message is a convention to nudge users towards using f-strings.
This closes #3592

[coveralls]

Pull Request Test Coverage Report for Build 1176970109

• 114 of 146 (78.08%) changed or added relevant lines in 43 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 92.746%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pylint/checkers/similar.py	1	2	50.0%
pylint/checkers/spelling.py	1	2	50.0%
pylint/checkers/strings.py	34	35	97.14%
pylint/config/option.py	0	1	0.0%
pylint/lint/run.py	0	1	0.0%
pylint/pyreverse/inspector.py	1	2	50.0%
pylint/pyreverse/utils.py	0	1	0.0%
pylint/reporters/base_reporter.py	0	1	0.0%
pylint/reporters/text.py	1	2	50.0%
pylint/reporters/ureports/nodes.py	1	2	50.0%

Files with Coverage Reduction	New Missed Lines	%
pylint/config/man_help_formatter.py	1	32.26%

Totals
Change from base Build 1169727876:	0.01%
Covered Lines:	13488
Relevant Lines:	14543

---

💛 - Coveralls

[DanielNoord]

Many changes in the second commit of this PR. However, I think they are warranted as f-strings are considerably faster, see here for example.
Let me know if anything needs to be changed!

[Pierre-Sassoulas]

Huge cleanup work alongside a very useful new checker, thanks a lot ! Did you check the change in performance by using the benchmark result locally ? If f-string are faster if could be another good news 😄 I have minor comments, let me know what you think.

[Pierre-Sassoulas]

Why remove this line ?

[DanielNoord]

I didn't think it added anything after line 8. Seems a duplicate

[DanielNoord]

Should be good to go now for 2.11.

I did not do the benchmarks, you might want to do them but I think there should be a performance increase. At least for some of the tests.

[Pierre-Sassoulas]

Thanks a lot, great checker and great clean up too !

[Pierre-Sassoulas]

Regarding the performance increase, I also think that it should increase because of f-string but we'd switch to f-string even with a sligth decrease in performance because of the readability and modernity :)

[cdce8p]

I don't think this should have been part of the StringChecker. It's only a recommendation, so at the very least this should go into the RecommendationChecker.

IMO this should even move to a new extension. str.format is still perfectly valid and in some cases even the more readable option!