Allow prerelease promotion to stable

[janechu]

Summary

• Allow stable change types on prerelease packages to promote to stable even when prereleasePrefix is configured.
• Add prepatch, preminor, and premajor to the interactive beachball change prompt.
• Update prerelease change-type documentation and the Beachball change-file skill guidance.

Validation

• yarn format ✅
• yarn format:check ✅
• cd packages/beachball && yarn test src/__tests__/bump/bumpPackageInfoVersion.test.ts src/__tests__/changefile/getQuestionsForPackage.test.ts src/__tests__/changefile/promptForChange.test.ts src/__tests__/changefile/promptForChange_promptForPackageChange.test.ts --runInBand ✅
• yarn checkchange ✅
• cd docs && yarn install --immutable && yarn docs:build ✅ (peer warnings only)
• yarn build ❌ pre-existing unrelated failure: src/monorepo/filterIgnoredFiles.ts(4,25): error TS2503: Cannot find namespace 'minimatch'.
• yarn test ❌ blocked by the same beachball#build failure.
• yarn lint ❌ lint:deps, lint:versions, and lint:marketplace passed; lint:code blocked by the same beachball#build failure.
• cd packages/beachball && yarn lint ❌ pre-existing unrelated warning in src/monorepo/filterIgnoredFiles.ts: unsafe minimatch.IOptions argument.

[ecraig12345]

Thanks for the PR--this is a change I'd like to make in some form, but it needs a lot more thought and would probably be part of an all-up rework of prerelease handling. See #1223 for links to some of the related issues.

One specific issue is that we shouldn't include the extra pre* change types by default--it would be confusing and unwanted for the overwhelming majority of beachball users, at least outside a major version bump. See #947 for more thoughts on this.