feat(react-components): move react-alert, react-infobutton, and react-virtualizer to optional peerDependencies

[dmytrokirpa]

This PR resolves React 19 peer dependency conflicts by moving @fluentui/react-alert,
@fluentui/react-infobutton, and @fluentui/react-virtualizer from direct dependencies to optional peer dependencies in the @fluentui/react-components package.

Problem

The deprecated packages exported through /unstable were causing peer dependency issues when
installing @fluentui/react-components with React 19:

WARN Issues with peer dependencies found

.
└─┬ @fluentui/react-components 9.70.0
  ├─┬ @fluentui/react-alert 9.0.0-beta.124
  │ ├── ✕ unmet peer react@">=16.14.0 <19.0.0": found 19.1.0
  │ ├── ✕ unmet peer react-dom@">=16.14.0 <19.0.0": found 19.1.0
  ├─┬ @fluentui/react-infobutton 9.0.0-beta.102
  │ ├── ✕ unmet peer react@">=16.14.0 <19.0.0": found 19.1.0
  │ ├── ✕ unmet peer react-dom@">=16.14.0 <19.0.0": found 19.1.0
  └─┬ @fluentui/react-virtualizer 9.0.0-alpha.102
    ├── ✕ unmet peer react@">=16.14.0 <19.0.0": found 19.1.0
    ├── ✕ unmet peer react-dom@">=16.14.0 <19.0.0": found 19.1.9

These packages:

• Are already deprecated and shouldn't be used in new projects
• Have been removed from the monorepo but remain as dependencies
• Don't support React 19 in their peer dependency ranges
• Are only kept for backward compatibility until the next major release

Solution

• Move the three problematic packages to optionalPeerDependencies
• This maintains backward compatibility for existing users who rely on /unstable exports
• Prevents installation issues for new users adopting React 19
• Aligns with the deprecation strategy - these packages are optional and discouraged

What Users Need to Do

• If you are not yet on React 19 and still use /unstable components:
  • You must manually install the relevant packages (@fluentui/react-alert, @fluentui/react-infobutton, or @fluentui/react-virtualizer) in your project.
• If you are migrating to React 19:
  • You should migrate away from /unstable exports, as these packages will not resolve peer dependencies with React 19 and manual installs will fail.

Benefits

• ✅ Enables smooth React 19 adoption without peer dependency conflicts
• ✅ Maintains backward compatibility for existing /unstable users
• ✅ Follows semantic versioning - no breaking changes
• ✅ Prepares for eventual removal in next major version

Testing

• Verified installation works with React 19 without peer dependency warnings
• Existing functionality remains unchanged for current users

This change supports the transition strategy for deprecated unstable components while enabling React 19 compatibility.