Allow providing replication slot on the CLI

[eminano]

The pgstream library already provides the ability to override the replication slot name. This PR adds the plumbing to allow setting it from the CLI.

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
pgstream/cmd	0.00% (ø)
pgstream/internal/postgres	0.00% (ø)
pgstream/pkg/stream	0.00% (ø)
pgstream/pkg/stream/integration	0.00% (ø)
pgstream/pkg/wal/replication/postgres	0.00% (ø)

---

Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
pgstream/cmd/config.go	0.00% (ø)	0	0	0
pgstream/cmd/init_cmd.go	0.00% (ø)	0	0	0
pgstream/cmd/root_cmd.go	0.00% (ø)	0	0	0
pgstream/internal/postgres/pg_replication_conn.go	0.00% (ø)	0	0	0
pgstream/pkg/stream/stream_init.go	0.00% (ø)	0	0	0
pgstream/pkg/wal/replication/postgres/pg_replication_handler.go	0.00% (ø)	0	0	0

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• pgstream/pkg/stream/integration/setup_test.go