feat(CORE): docker permissions and rework (#13454)

- fix docker permissions with mounted volumes on new docker versions (https://github.com/docker/desktop-linux/issues/31)
- fix ac-tools image
- cleanup unused env
- add  `cap_add: SYS_NICE` to allow setting process high priority
- fix ccache in docker
- allow to switch between root user (default) to acore user in any container
- fix cache of the downloaded client data
- split docker github actions in 2 parts
- versioning mysql images
- performance improvements

.github/workflows/import_pending.yml

@@ -9,7 +9,7 @@ jobs:
     strategy:
       fail-fast: false
     runs-on: ubuntu-20.04
-    if: github.repository == 'azerothcore/azerothcore-wotlk'
+    if: github.repository == 'azerothcore/azerothcore-wotlk' && !github.event.pull_request.draft
     steps:
       - uses: actions/checkout@v2
         with: