MudInput: Fix FullWidth not applied

[omarkurtovic]

Closes #6341

Hello,
MudInput was not filling the parent container because the outer div that the component renders did not have a width style applied. By adding the "mud-input-full-width" class to the div it is now expanding to fill the avaliable space correctly.

chrome_bdYk4aWYGb.mp4

Checklist:

• I've read the contribution guidelines
• My code follows the style of this project
• I've added or updated relevant unit tests

[danielchalmers]

Thank you!