feat(input): add counter and counterFormatter

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue URL: N/A

It is not possible to specify a counter or counterFormatter on ion-input.

What is the new behavior?

• Added support for showing maxlength counter text via counter.
• Added support for showing a custom formatter text via counterFormatter.
• Deprecated the counter and counterFormatter properties on ion-item.
• Added tests

Note: I am still missing some padding/margin styles so the screenshots will likely change again before the larger migration is complete (correctly making the style updates requires more of the input functionality to be migrated.) These changes will be made in a future PR.

Does this introduce a breaking change?

• Yes
• No

Other information