Move beats metadata script to timelines plugin

This is the plugin that consumes the artifacts of the script, not
security_solution.

x-pack/plugins/security_solution/package.json

@@ -6,7 +6,6 @@
   "license": "Elastic-License",
   "scripts": {
     "extract-mitre-attacks": "node scripts/extract_tactics_techniques_mitre.js && node ../../../scripts/eslint ./public/detections/mitre/mitre_tactics_techniques.ts --fix",
-    "build-beat-doc": "node scripts/beat_docs/build.js && node ../../../scripts/eslint ./server/utils/beat_schema/fields.ts --fix",
     "cypress": "../../../node_modules/.bin/cypress",
     "cypress:open": "yarn cypress open --config-file ./cypress/cypress.json",
     "cypress:open:ccs": "yarn cypress:open --config integrationFolder=./cypress/ccs_integration",

x-pack/plugins/timelines/package.json

@@ -0,0 +1,10 @@
+{
+  "author": "Elastic",
+  "name": "timelines",
+  "version": "8.0.0",
+  "private": true,
+  "license": "Elastic-License",
+  "scripts": {
+    "build-beat-doc": "node scripts/beat_docs/build.js && node ../../../scripts/eslint ./server/utils/beat_schema/fields.ts --fix"
+  }
+}