fix: determine region role by using is_readonly #19804

Job	Run time
Build GreptimeDB binaries (ubuntu-20.04)	3m 2s
Check (windows-2022)	9m 44s
Check (ubuntu-20.04)	2m 10s
Check typos and docs	6s
Build GreptimeDB binary (profile-CI) (ubuntu-20.04)	2m 51s
Clippy	3m 37s
coverage	13m 49s
Rustfmt	39s
Check License Header	2m 11s
Toml Check	2m 18s
Unstable Fuzz Test (unstable_fuzz_create_table_standalone)	7m 4s
Fuzz Test (Distributed, Remote WAL, fuzz_create_table)	8m 27s
Fuzz Test with Chaos (Distributed, Remote WAL, fuzz_migrate_mito_regions)	8m 10s
Fuzz Test (Distributed, Remote WAL, fuzz_alter_table)	7m 8s
Fuzz Test with Chaos (Distributed, Remote WAL, fuzz_failover_mito_regions)	8m 0s
Fuzz Test (Distributed, Remote WAL, fuzz_create_database)	8m 1s
Fuzz Test with Chaos (Distributed, Remote WAL, fuzz_failover_metric_regions)	7m 27s
Fuzz Test (Distributed, Remote WAL, fuzz_create_logical_table)	6m 25s
Fuzz Test (Distributed, Remote WAL, fuzz_alter_logical_table)	6m 35s
Fuzz Test (Distributed, Remote WAL, fuzz_insert)	7m 47s
Fuzz Test (Distributed, Remote WAL, fuzz_insert_logical_table)	6m 57s
Sqlness Test (Basic)	2m 42s
Fuzz Test (fuzz_create_table)	3m 58s
Sqlness Test (Remote WAL)	2m 52s
Fuzz Test (fuzz_alter_table)	4m 19s
Fuzz Test (fuzz_create_database)	4m 0s
Fuzz Test (fuzz_create_logical_table)	4m 18s
Fuzz Test (fuzz_alter_logical_table)	5m 16s
Fuzz Test (fuzz_insert)	5m 14s
Fuzz Test (fuzz_insert_logical_table)	4m 20s
	2h 39m 27s

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