gh-113317: Remove Argument Clinic global variable 'clinic'

[vstinner]

• Add Clinic.warn() and Clinic.fail() methods.
• Add filename parameter to BlockParser constructor.
• Add BlockParser.fail() method.
• Add DSLParser.fail() method.
• Pass lineno parameter to DSLParser.format_docstring(): more accurate error reporting.
• Convert a few DSLParser static methods to regular method to be able to call self.fail().
• Language.render() clinic parameter is now required: None is no longer accepted.
• Remove warn() function.
• Remove global variable 'clinic'.

fail() and warn() methods get filename and line number from the instance on which the method is called, rather than relying on a global variable 'clinic'.

• Issue: Argument Clinic: split out global stateless helpers and constants from clinic.py #113317

[vstinner]

@erlend-aasland@AlexWaygood: Would you mind to review this change?

@erlend-aasland wrote a different approach: Argument-Clinic#35

[vstinner]

See also Argument-Clinic#36

[AlexWaygood]

I'm stepping down as an AC maintainer for now :) #114796

I trust you two to come to the right decision!

[vstinner]

I'm stepping down as an AC maintainer for now :) #114796

Even if you're not officially an "expert" or "code owner", your opinion still matters for me, and you're free to pick some reviews whenever you want. But I understand that I should ping you less often on such AC changes ;-)

[vstinner]

Ping @erlend-aasland: Gentle reminder that I'm looking for a review :-)

[erlend-aasland]

Superseded by #115517.