Remove true-case-path

[tivac]

Description

Removing true-case-path package from @modular-css/processor and replaced it with a new dupewarn option that defaults to true.

Motivation and Context

Fixes #581, adding a warning and removing the checks entirely is simpler and reasonably safe for all the cases that caused true-case-path to be added in the first place (#191, #527)

How Has This Been Tested?

Added tests to make sure the warning correctly triggers and can be disabled.

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 change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

THIS IS A BREAKING CHANGE

[codecov]

Codecov Report

Merging #582 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #582      +/-   ##
==========================================
+ Coverage    98.9%   98.92%   +0.01%     
==========================================
  Files          47       48       +1     
  Lines        1191     1211      +20     
  Branches      183      184       +1     
==========================================
+ Hits         1178     1198      +20     
  Misses         13       13

Impacted Files	Coverage Δ
packages/rollup-rewriter/formats/amd.js	92.85% <100%> (+3.96%)	⬆️
packages/rollup-rewriter/rewriter.js	100% <100%> (ø)	⬆️
packages/processor/processor.js	100% <100%> (ø)	⬆️
packages/processor/lib/normalize.js	100% <100%> (ø)	⬆️
packages/test-utils/case-sensitive-fs.js	100% <100%> (ø)
packages/test-utils/read-dir.js	100% <100%> (ø)	⬆️
packages/processor/lib/resolve.js	100% <100%> (ø)	⬆️
packages/rollup-rewriter/formats/system.js	91.66% <100%> (+2.77%)	⬆️
packages/rollup-rewriter/formats/es.js	100% <100%> (ø)	⬆️

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