fix(webpack): alias react-checkbox-tree to its ESM bundle (#9989)

react-checkbox-tree v2 marks the package as "type": "module" but its
"require" exports condition still points at a UMD bundle. babel-loader
turns our ESM imports into require() calls, so webpack picks the UMD
file and treats it as ESM (because of "type": "module"). The UMD
wrapper's module.exports = factory(...) never runs in that context, and
the default export ends up undefined - causing CheckBoxTree to render
"Element type is invalid" in dialogs like Import/Export Servers.

Alias react-checkbox-tree to its ESM bundle (lib/index.esm.js, exposed
by the package's own "./*": "./*" exports map) so webpack picks the file
that actually has a default export.

Closes #9972