chore: use github var for kurrentdb images #785

Job	Run time
Build (8)	42s
Build (11)	58s
Build (17)	49s
Tests (LTS) / Cluster (Streams)	5s
Tests (CI) / Secure (Streams)	7s
Tests (CI) / Single node (Streams)	6s
Tests (LTS) / Cluster (PersistentSubscriptions)	6s
Tests (CI) / Cluster (Streams)	4s
Tests (CI) / Secure (PersistentSubscriptions)	5s
Tests (CI) / Single node (PersistentSubscriptions)	10s
Tests (CI) / Cluster (PersistentSubscriptions)	5s
Tests (CI) / Single node (Telemetry)	6s
Tests (LTS) / Secure (Streams)	8s
Tests (LTS) / Single node (Streams)	6s
Tests (LTS) / Secure (PersistentSubscriptions)	6s
Plugins Tests / Cluster (Plugins)	1m 18s
Tests (LTS) / Single node (PersistentSubscriptions)	9s
Plugins Tests / Single Node (Plugins)	8m 0s
Tests (LTS) / Single node (Telemetry)	5s
Tests (Previous LTS) / Cluster (Streams)	4s
Tests (Previous LTS) / Single node (Streams)	9s
Tests (Previous LTS) / Cluster (PersistentSubscriptions)	7s
Tests (Previous LTS) / Secure (Streams)	5s
Tests (Previous LTS) / Single node (PersistentSubscriptions)	5s
Tests (Previous LTS) / Secure (PersistentSubscriptions)	10s
Tests (Previous LTS) / Single node (Telemetry)	9s
	14m 4s

Provide feedback