Follow-up on #132

We've an agreement on the structure proposal in #137 , so here is the list of next action items:

• elastic-package: update the package-spec with changes in Support input groups #137 and point no. 1 (integrity between data streams) - Update package-spec to support input groups elastic-package#267
• package-spec: enforce referential integrity between data_streams mentioned in policy template items and folders under <package root>/data_stream/ - Ensure integrity between input groups and data streams #143
• integrations: update elastic-package - Enable static test runner integrations#754
• elastic-package: build multiple README files - Check and generate multiple readme files in one package elastic-package#282
• integrations: modify the AWS package to use input groups (merge only if Kibana and Package Registry support it) Adjust aws package to use input groups integrations#767
• package-registry: support input groups, check with the modified AWS package Add input groups support  package-registry#685
• kibana: support input groups [Fleet] Integration input groups, phase 1 kibana#93315
• package-storage: release the package