build: migrate to webpack@5

[char0n]

Refs #2944
Succeeded #2949
Succeeded #2976

Description

I made minimal changes that were required to migrate to webpack@5. Some changes were taken from #2949 and #2976.

Additional notes:

• worker-loader still works with webpack@5 and is the only way how to inline the web worker or set other advanced web worker settings
• validation.worker - we always want web worker to be inlined for simplicity and backward compatibility
• we don't use fallback anymore in all cases, as we don't care about very old browsers that don't support web workers anymore (IE 11)
• fought through Error: Can't resolve './defineProperty' reduxjs/redux#4174 which was resolved by regenerating package-lock file

Overcomed: reduxjs/redux#4174

How Has This Been Tested?

Manually. Still needs to test if primary build bundle works with webpack@4 and webpack@5.

Screenshots (if appropriate):

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.

[tim-lai]

@char0n approving PR. just need to fix merge conflict(s). Also a note to confirm Docker build after merge. Also a sidenote, fyi, and was not intending to fix in this PR, is how to handle including worker sourcemap with different outputs, related to this ticket: #2146

[char0n]

I'll address your feedback on Monday next week and ideally on Tuesday we'll go for a merge.

[char0n]

Rebased on top of current master.

[char0n]

@tim-lai transformed your feedback to additional todo list in https:/swagger-api/oss-planning/issues/550