Add tally of fixable problems to string and verbose formatters

[m-allanson]

Which issue, if any, is this issue related to?

Closes #7338

Is there anything in the PR that needs further explanation?

This PR adds a count of potentially fixable problems to the string formatter's output. e.g.

file.css
  1:2  ×  Unexpected foo  no-foo
  1:2  ×  Unexpected bar  no-bar
  1:2  ‼  Unexpected baz  no-baz

× 3 problems (2 errors, 1 warning)
  1 error and 1 warning potentially fixable with the "--fix" option.

The line 1 error and 1 warning potentially fixable with the "--fix" option. is new.

In adddition, I've adjusted the formatting slighty, to ensure that the most important line (the problem count) is still visually distinct. This new formatting imitates eslint's default output.

The formatting changes are:

• add an × in front of the problem count, to highlight that line
• indent the list of problems, so that the line numbers are vertically aligned with the problem count and fix count text.

Formatting examples

Here are examples of the formatting changes, excluding the new fixable counts.

Old formatting:

file.css
 1:2  ×  Unexpected foo  no-foo
 1:2  ×  Unexpected bar  no-bar
 1:2  ‼  Unexpected baz  no-baz

3 problems (2 errors, 1 warning)

New formatting:

file.css
  1:2  ×  Unexpected foo  no-foo
  1:2  ×  Unexpected bar  no-bar
  1:2  ‼  Unexpected baz  no-baz

× 3 problems (2 errors, 1 warning)

[changeset-bot]

🦋 Changeset detected

Latest commit: ef51335

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
stylelint	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[ybiquitous]

@m-allanson Thanks for the pull request.

• add an × in front of the problem count, to highlight that line

That sounds good to me. But I am concerned about a case of 0 errors and some warnings, e.g.

file.css
 1:2  ‼  Unexpected baz  no-baz

× 1 problem (0 errors, 1 warning)

In this case, using ‼ instead of × seems a bit more consistent and readable for me. What do you think?

[m-allanson]

Thanks for the review @ybiquitous 👍 This is updated and ready for another look.

[ybiquitous]

Thank you. This PR is almost okay. But I just commented on a refactoring, so can you take a look?

[ybiquitous]

Thanks! LGTM 👍🏼

[Mouvedia]

The tests look good to me.