fix(makeStyles): Fix object literal outside useMemo causing styles to change on every render

[duncannz]

Motivation

We found that the return value of makeStyles was changing on every render, which impacts performance, and makes it impossible to use it as a dependency of useMemo etc. without getting a "maximum update depth exceeded" error.

This change resolves this issue by ensuring the empty object literal used when no props are given is created inside the useMemo.

Type of change

• 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)
• This change requires a documentation update

How Has This Been Tested?

• Jest Unit Test
• Checked with example app

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation using yarn docs-build-api
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Additional context

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (cec04af) 79.71% compared to head (55295d2) 79.68%.

Files	Patch %	Lines
packages/themed/src/config/makeStyles.ts	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #3844      +/-   ##
==========================================
- Coverage   79.71%   79.68%   -0.04%     
==========================================
  Files          87       87              
  Lines        1844     1846       +2     
  Branches      821      803      -18     
==========================================
+ Hits         1470     1471       +1     
- Misses        369      370       +1     
  Partials        5        5              

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