Allow mounting a volume to host the config and enable read only root FS #1603

Job	Run time
Build Reaper	7m 24s
Docker Image Tests (cassandra, docker)	7m 46s
HTTP Management (binary:4.0.6, ccm, http-api, 1, 1)	23m 56s
Memory backends (binary:3.0.25, local, ccm)	17m 50s
HTTP Management (binary:3.11.16, ccm, http-api, 1, 1)	24m 26s
Cassandra backend (binary:3.0.25, cassandra, ccm)	19m 14s
Memory backends (binary:3.11.16, local, ccm)	17m 50s
Cassandra backend (binary:3.11.16, cassandra, ccm)	21m 39s
Memory backends (binary:4.0.6, local, ccm)	22m 8s
Cassandra backend (binary:4.0.6, cassandra, ccm)	25m 0s
Each DC Availability (binary:4.0.6, cassandra, each, 1, 1)	19m 35s
Flapping reapers (binary:4.0.6, cassandra, ccm, 4, 2, --tags ~@diag_event_subscriptions)	23m 51s
Distributed tests (binary:3.0.25, cassandra, ccm, 2, 2)	20m 23s
Sidecar (binary:3.0.25, cassandra, sidecar, 1, 1)	17m 30s
Distributed tests (binary:3.11.16, cassandra, ccm, 2, 2)	26m 41s
Distributed tests (binary:4.0.6, cassandra, ccm, 2, 2)	24m 43s
Sidecar (binary:3.11.16, cassandra, sidecar, 1, 1)	16m 28s
Sidecar (binary:4.0.6, cassandra, sidecar, 1, 1)	18m 43s
Release Reaper	0s
	5h 55m 7s

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