Add format customization flow to `click.prompt` and `click.confirm` via `PromptBuilder` class

[AdamPiotrowski91]

This PR implements a base class which allows to customize prompt format when used directly via click.prompt or click.confirm methods.

It adds an optional parameter which can be an instance of a PromptBuilder class or one inheriting from it.

You can customize all of the below in any combination:

• how the prompt is built via overriding build method
• how the choices are shown via overriding add_choices method
• how the default is shown via overriding add_default method
• how to calculate if choices should be shown via overriding should_add_choices method
• how to calculate if default should be shown via overriding should_add_default method

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fixes #2875

[AdamPiotrowski91]

Tests pass, but I am not sure, based on the logs, why do the other jobs fail. Would appreciate some help in this regard.