fix: config api and export metrics default database #19412

Job	Run time
Toml Check	28s
Check typos and docs	7s
Build GreptimeDB binary (profile-CI) (ubuntu-20.04)	3m 15s
Build GreptimeDB binaries (ubuntu-20.04)	3m 0s
Check (windows-2022)	8m 37s
Clippy	3m 33s
Rustfmt	39s
Check (ubuntu-20.04)	2m 19s
Check License Header	2m 16s
coverage	0s
Fuzz Test (fuzz_create_table)	6m 31s
Fuzz Test (fuzz_alter_table)	8m 0s
Sqlness Test (Basic)	2m 31s
Fuzz Test (fuzz_create_database)	6m 14s
Fuzz Test (fuzz_create_logical_table)	6m 12s
Sqlness Test (Remote WAL)	2m 54s
Fuzz Test (fuzz_alter_logical_table)	7m 11s
Fuzz Test (fuzz_insert)	6m 10s
Fuzz Test (fuzz_insert_logical_table)	6m 31s
Unstable Fuzz Test (unstable_fuzz_create_table_standalone)	5m 37s
Fuzz Test (Distributed, Remote WAL, fuzz_create_table)	8m 41s
Fuzz Test with Chaos (Distributed, Remote WAL, fuzz_migrate_mito_regions)	7m 9s
Fuzz Test (Distributed, Remote WAL, fuzz_alter_table)	9m 0s
Fuzz Test with Chaos (Distributed, Remote WAL, fuzz_failover_mito_regions)	8m 16s
Fuzz Test (Distributed, Remote WAL, fuzz_create_database)	8m 28s
Fuzz Test with Chaos (Distributed, Remote WAL, fuzz_failover_metric_regions)	8m 3s
Fuzz Test (Distributed, Remote WAL, fuzz_create_logical_table)	8m 34s
Fuzz Test (Distributed, Remote WAL, fuzz_alter_logical_table)	9m 2s
Fuzz Test (Distributed, Remote WAL, fuzz_insert)	8m 41s
Fuzz Test (Distributed, Remote WAL, fuzz_insert_logical_table)	9m 53s
	2h 47m 52s

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