feat: use own CancellationToken class

[mrazauskas]

Using own CancellationToken class allows lowering requirements for Node.js (and slightly simplifies logic).

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.09% (target: -1.00%)	✅ 96.40%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (22719ad)	5277	5119	97.01%
Head commit (bee3e64)	5273 (-4)	5120 (+1)	97.10% (+0.09%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#135)	111	107	96.40%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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