test: migrate the package template to Vitest

[cryptodev-2s]

Explanation

Migrate package-template to vitest.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
  • Not applicable, test only change to a private template package. Carries the no-changelog label.
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them
  • None.

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Note

Low Risk
Test-only tooling change on a private template package; no runtime or consumer API impact.

Overview
Migrates @metamask/package-template from Jest to Vitest, aligning the scaffold package with the repo’s default test runner for new packages.

Jest is removed (jest.config.cjs, Jest-related devDependencies, and NODE_OPTIONS=--experimental-vm-modules test scripts). Tests now run via Vitest (vitest.config.mjs merged from vitest.config.packages.mjs, with the same 100% coverage thresholds). The sample test imports describe / expect / it from vitest, and tsconfig.json sets compilerOptions.types to [] so repo-wide Jest types do not apply.

@metamask/package-template is dropped from the Jest list in test-runner-package-map.cjs, and the oxlint suppression for the deleted Jest config is cleaned up.

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