refactor: use dedicated regex methods

[sapphi-red]

Description

• use hasIndices flag (d)
• foo.slice(ops).match(regex) -> regex.lastIndex = pos; regex.exec(foo)
• !!foo.match(regex) -> regex.test(foo)
• !!foo.match(string) -> foo.includes(string)
• foo.match(regex)?.index -> foo.search(regex)
• regex.test() -> .startsWith()/.endsWith()/.includes()
• expect(foo.match(string)).toBeNull() -> expect(foo).toContain(string)
• (fix) add .lastIndex = 0 before /something/g.test(something)

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines, especially the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Update the corresponding documentation if needed.
• Ideally, include relevant tests that fail without this PR but pass with it.

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[patak-dev]

Great stuff!