MudInput: Add class when AutoGrow is enabled

[danielchalmers]

Description

Simply adds a class to MudInput if AutoGrow is enabled for more extensibility.

How Has This Been Tested?

unit

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)

Checklist:

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.
• I've added relevant tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.74%. Comparing base (ee80e01) to head (e03254f).
Report is 59 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8234      +/-   ##
==========================================
+ Coverage   88.25%   88.74%   +0.48%     
==========================================
  Files         394      407      +13     
  Lines       11742    12187     +445     
  Branches     2377     2429      +52     
==========================================
+ Hits        10363    10815     +452     
+ Misses        854      847       -7     
  Partials      525      525              

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