fix: config api and export metrics default database #19411

Job	Run time
Check (windows-2022)	1m 15s
Check typos and docs	11s
Check (ubuntu-20.04)	1m 25s
Check License Header	1m 23s
Toml Check	33s
Build GreptimeDB binaries (ubuntu-20.04)	1m 22s
Build GreptimeDB binary (profile-CI) (ubuntu-20.04)	1m 24s
Clippy	1m 24s
Rustfmt	35s
coverage	1m 9s
Unstable Fuzz Test	1s
Fuzz Test (Distributed, ${{ matrix.mode.name }}, ${{ matrix.target }})	1s
Fuzz Test with Chaos (Distributed, ${{ matrix.mode.name }}, ${{ matrix.target }})	1s
Fuzz Test	1s
Sqlness Test (${{ matrix.mode.name }})	1s
	10m 46s

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