Grafana UI: Expose unstable entrypoint (#97080)

* feat(grafana-ui): build unstable entrypoint for experimental components

* feat(plugins): expose grafana/ui/unstable

* build(grafana-ui): add rollup plugin to create alias package.json for unstable entrypoint

* build(packages): rewrite prepare npm script to generate alias packagejson files

* chore(packages): use relative paths in publishConfig for exports generation

* chore(frontend): move npmcli/package-json package to root package.json

* revert(grafana-ui): remove rollup plugin for generating alias package.json files

* chore(grafana-ui): clean up unstable directory postpack to prevent yarn lock issues

* build(packages): fix scope for pkgName usage

* feat(packages): create separate cjs and esm builds that validate with arethetypeswrong cli

* chore(yarn): refresh lock file

* fix(packages): make sure alias package.jsons point to existing files

.gitignore

@@ -148,6 +148,7 @@ pkg/services/quota/quotaimpl/storage/storage.json
 # Ignoring frontend packages specifics
 /packages/grafana-ui/.yarn/.cache
 /packages/grafana-ui/.storybook/static
+/packages/grafana-ui/unstable
 /packages/**/dist
 /packages/**/compiled
 /packages/**/.rpt2_cache