refactor(input): remove legacy property and support for legacy syntax

[brandyscarney]

Issue number: internal

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What is the current behavior?

In Ionic Framework v7, we simplified the input syntax so that it was no longer required to be placed inside of an ion-item. We maintained backwards compatibility by adding a legacy property which allowed it to continue to be styled properly when written in the following way:

<ion-item>
  <ion-label>Label</ion-label>
  <ion-input></ion-input>
</ion-item>

While this was supported in v7, console warnings were logged to notify developers that they needed to update this syntax for the best accessibility experience.

What is the new behavior?

• Removes the legacy property and support for the legacy syntax. Developers should follow the migration guide in the input documentation to update their apps. The new syntax requires a label or aria-label on ion-input:

  <ion-item>
    <ion-input label="Label"></ion-input>
  </ion-item>

• Removes the legacy tests under under input/test/legacy/ and all related screenshots
• Removes the input usage from item/test/a11y, item/test/counter, item/test/disabled, item/test/highlight, item/test/legacy/alignment, item/test/legacy/disabled, item/test/legacy/fill, and item/test/legacy/form and all related screenshots if the test was removed

Does this introduce a breaking change?

• Yes
• No

1. Developers have had console warnings when using the legacy syntax since the v7 release. The migration guide for the new input syntax is outlined in the Input documentation.
2. This change has been documented in the Breaking Changes document with a link to the migration guide.

BREAKING CHANGE:

The legacy property and support for the legacy syntax, which involved placing an ion-input inside of an ion-item with an ion-label, have been removed from input. For more information on migrating from the legacy input syntax, refer to the Input documentation.