feat!: next.js 15, react 19, react compiler support (#6429)

**BREAKING:**
- bumps minimum required next.js version from `14.3.0-canary.68` to
`15.0.0-rc.0`
- bumps minimum required react and react-dom versions to `19.0.0
`(`19.0.0-rc-f994737d14-20240522` should be used)
- `@types/react` and `@types/react-dom` have to be bumped to
`npm:types-react@19.0.0-beta.2` using overrides and pnpm overrides, if
you want correct types. You can find an example of this here:
https://github.com/payloadcms/payload/pull/6429/files#diff-10cb9e57a77733f174ee2888587281e94c31f79e434aa3f932a8ec72fa7a5121L32

## Issues

- Bunch of todos for our react-select package which is having type
issues. Works fine, just type issues. Their type defs are importing JSX
in a weird way, we likely just have to wait until they fix them in a
future update.