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

.github/CODEOWNERS

@@ -620,7 +620,7 @@ playwright.config.ts @grafana/plugins-platform-frontend
 /scripts/import_many_dashboards.sh @torkelo
 /scripts/mixin-check.sh @bergquist
 /scripts/openapi3/ @grafana/grafana-operator-experience-squad
-/scripts/prepare-packagejson.js @grafana/frontend-ops
+/scripts/prepare-npm-package.js @grafana/frontend-ops
 /scripts/protobuf-check.sh @grafana/plugins-platform-backend
 /scripts/stripnulls.sh @grafana/grafana-as-code
 /scripts/tag_release.sh @grafana/grafana-developer-enablement-squad