revert(VTextField): only show clear icon on hover or when focused

[vchrisb]

Description

This is reverting commit 7a51ad0 and therefore a fix for #15830.

Motivation and Context

The change to only show the clear icon on hover or when focused in VTextField isn't a desired change in UX and breaking usability on touch devices.
It is not obvious in first sight that the VTextField can be cleared (e.g. if VTextField was prefilled) and on touch devices two touches are required.

How Has This Been Tested?

it is a revert

Markup:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement/refactoring (non-breaking change that doesn't add any features but makes things better)

Checklist:

• The PR title is no longer than 64 characters.
• The PR is submitted to the correct branch (master for bug fixes and documentation updates, dev for new features and backwards compatible changes and next for non-backwards compatible changes).
• My code follows the code style of this project.
• I've added relevant changes to the documentation (applies to new features and breaking changes in core library)