MudContainer: Add Gutters property

[danielchalmers]

Description

I use the MudContainer and currently have to override the styles to avoid the extra padding added. This lets you control it with a property like several other controls.

Interestingly there was an unused mud-container-disable-gutters, but I reversed the way the padding is handled in a fashion like #8586. Normally it's added then removed but this way it's only added if Gutters is actually enabled in the first place. This should be the general convention IMO because it avoid usage of !important which messes with consumers' overrides.

How Has This Been Tested?

unit, visually

Type 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)
• Documentation (fix or improvement to the website or code docs)

Default vs Gutters=false

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 90.45%. Comparing base (28bc599) to head (6d70680).
Report is 176 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8934      +/-   ##
==========================================
+ Coverage   89.82%   90.45%   +0.62%     
==========================================
  Files         412      419       +7     
  Lines       11878    12190     +312     
  Branches     2364     2380      +16     
==========================================
+ Hits        10670    11026     +356     
+ Misses        681      630      -51     
- Partials      527      534       +7     

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