chore(release): Drop build numbers from versions and update melos to 8.4.0

[spydon]

Description

Removes the +x build numbers from all package versions and updates melos to ^8.4.0.

Every +x version was the currently published one on pub.dev, so plain stripping would have produced versions that sort lower than what is published. Each package got a patch bump instead, with the build number dropped:

Package	Before	After
gamepads_android	0.1.8+2	0.1.9
gamepads_darwin	0.1.2+4	0.1.3
gamepads_ios	0.1.3+3	0.1.4
gamepads_web	0.1.1+1	0.1.2
gamepads_windows	0.3.0+1	0.3.1
gamepads	0.1.10+5	0.1.11
flutter_gamepads	0.1.11+4	0.1.12

Internal dependency constraints and changelogs were generated with melos version from the unreleased commits (#125 to #129). gamepads_web and gamepads_windows had no unreleased changes and are only bumped to drop the suffix.

Melos 8.x bumps the patch version for fixes and dependency updates on 0.x packages and only keeps a build number when the current version already has one, so with these clean versions no +x will be reintroduced by future melos version runs. 8.4.0 is the latest release and requires sdk: ^3.9.0, which matches the workspace minimum.

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

https://claude.ai/code/session_01ECm9j87ohzVbQSagq7qe8M