fix: replace backslashes with forward slashes in refs on Windows when splitting

[tatomyr]

What/Why/How?

• Replaced backslashes in file paths on Windows
• Moved smoke preparation scripts to the corresponding folder

NB: When reviewing, you can ignore files in the __tests__/smoke/pre-split folder as they are simply example splits of museum.yaml and pets.yaml. The actual fix is here.

Reference

Fixes #638

Testing

Added a smoke test.

Screenshots (optional)

Check yourself

• Code changed? - Tested with redoc/reference-docs/workflows (internal)
• All new/updated code is covered with tests
• New package installed? - Tested in different environments (browser/node)

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

[changeset-bot]

🦋 Changeset detected

Latest commit: 95eb738

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@redocly/cli	Patch
@redocly/openapi-core	Patch

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[github-actions]

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
redocly lint packages/core/src/benchmark/benches/rebilly.yaml	954.6 ± 21.9	932.3	999.2	1.00
redocly-next lint packages/core/src/benchmark/benches/rebilly.yaml	961.0 ± 16.0	944.0	996.9	1.01 ± 0.03

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	78.54%	5062/6445
🟡	Branches	67.24%	2065/3071
🟡	Functions	73.2%	836/1142
🟡	Lines	78.82%	4775/6058

Test suite run success

839 tests passing in 121 suites.

Report generated by 🧪jest coverage report action from 95eb738