fix(input): item and clear input styling is correct

[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?

Using the modern input inside of an item caused incorrect padding to render. Also, the highlight line was partially obscured by the item's line.

Additionally, the clear input button was misaligned

What is the new behavior?

• The clear input button is now aligned correctly at the end of the line
• The end padding on ion-item is removed when using the modern input
• The highlight is now visible in ion-item when using the modern input
• Add TODOs for cleaning up legacy input

Note: I also added a few tests that looks at all of ion-input when using the bottom content. It's 3 tests so I added it while working on this fix. Let me know if you'd prefer that be in a separate PR though.

Does this introduce a breaking change?

• Yes
• No

Other information