refactor(log_store): remove associated type `Namespace` and `Entry` in `LogStore` #16791

Job	Run time
Toml Check	22s
Check typos and docs	7s
Build GreptimeDB binaries (ubuntu-20.04)	4m 10s
Build GreptimeDB binary (profile-CI) (ubuntu-20.04)	2m 27s
Check (windows-2022)	7m 21s
Clippy	3m 9s
Check (ubuntu-20.04)	1m 39s
Rustfmt	25s
Check License Header	1m 19s
coverage	13m 18s
Fuzz Test (Distributed, Disk) (fuzz_create_table)	7m 10s
Fuzz Test (Distributed, Disk) (fuzz_alter_table)	6m 48s
Fuzz Test (Distributed, Disk) (fuzz_create_database)	7m 35s
Fuzz Test (Distributed, Disk) (fuzz_create_logical_table)	7m 15s
Fuzz Test (Distributed, Disk) (fuzz_alter_logical_table)	7m 2s
Fuzz Test (Distributed, Disk) (fuzz_insert)	6m 42s
Fuzz Test (Distributed, Disk) (fuzz_insert_logical_table)	7m 34s
Unstable Fuzz Test (unstable_fuzz_create_table_standalone)	13m 36s
Sqlness Test (ubuntu-20.04)	2m 28s
Sqlness Test with Kafka Wal (ubuntu-20.04)	3m 18s
Fuzz Test (fuzz_create_table)	9m 14s
Fuzz Test (fuzz_alter_table)	5m 34s
Fuzz Test (fuzz_create_database)	5m 20s
Fuzz Test (fuzz_create_logical_table)	5m 34s
Fuzz Test (fuzz_alter_logical_table)	6m 1s
Fuzz Test (fuzz_insert)	5m 10s
Fuzz Test (fuzz_insert_logical_table)	5m 50s
	2h 26m 28s

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