feat: remove sync engine, sessiond and `get_db` function #6506

Job	Run time
Check source changes / Check repo files	9s
Check if must build & deploy from environment	1s
Run extra tests (training, monitoring and listeners) / Argilla python tests	10m 51s
Run base tests (docker.elastic.co/elasticsearch/elasticsearch:7.17.11, {"discovery.type": "single... / Argilla python tests	11m 32s
Run base tests (docker.elastic.co/elasticsearch/elasticsearch:8.8.2, {"discovery.type": "single-n... / Argilla python tests	10m 53s
Run base tests (docker.elastic.co/elasticsearch/elasticsearch:8.0.1, {"discovery.type": "single-n... / Argilla python tests	10m 31s
Run base tests (opensearchproject/opensearch:1.3.11, {"discovery.type": "single-node", "plugins.s... / Argilla python tests	10m 12s
Run base tests (opensearchproject/opensearch:2.4.1, {"discovery.type": "single-node", "plugins.se... / Argilla python tests	10m 28s
Build Argilla python package / Build the python package	4m 39s
Upload code coverage	17s
Build Argilla server docker image / Build Docker image	10m 16s
Build Argilla quickstart docker image / Build Docker image	6m 41s
Deploy Release	0s
	1h 26m 30s

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