Build: Nx improvements (#88341)

* feat(frontend): introduce project.json for every workspace to improve caching

* refactor(frontend): use nx tags for grafana dependson

* refactor(frontend): clean up nx tags for packages and plugins

* build(nx): make grafana dependent on cacheable generate icons command

* build(nx): clean up project files

project.json

@@ -6,8 +6,9 @@
     "start": {
       "dependsOn": [
         "themes-generate",
+        "grafana-icons:generate",
         {
-          "projects": ["@grafana-plugins/**"],
+          "projects": ["tag:scope:plugin"],
           "target": "build"
         }
       ]
@@ -15,8 +16,9 @@
     "build": {
       "dependsOn": [
         "themes-generate",
+        "grafana-icons:generate",
         {
-          "projects": ["@grafana-plugins/**"],
+          "projects": ["tag:scope:plugin"],
           "target": "build"
         }
       ],