feat: databend-meta adds more metrics about raft-log

[drmingdrmer]

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Summary

feat: databend-meta adds more metrics about raft-log

• "raft_log_cache_items" : number of items in raft log cache;
• "raft_log_cache_used_size" : size of used space in raft log cache;
• "raft_log_wal_open_chunk_size" : size of open chunk in raft log wal;
• "raft_log_wal_offset" : global offset of raft log WAL;
• "raft_log_wal_closed_chunk_count" : number of closed chunks in raft log WAL;
• "raft_log_wal_closed_chunk_total_size" : total size of closed chunks in raft log WAL;

Example output of these new metrics:

metasrv_server_raft_log_cache_items                 35496
metasrv_server_raft_log_cache_used_size             659024620
metasrv_server_raft_log_wal_open_chunk_size         803
metasrv_server_raft_log_wal_offset                  3536913654
metasrv_server_raft_log_wal_closed_chunk_count      3
metasrv_server_raft_log_wal_closed_chunk_total_size 584045971
metasrv_server_raft_log_size                        584046774

Tests

• [x] Unit Test
• [ ] Logic Test
• [ ] Benchmark Test
• [ ] No Test - Explain why

Type of change

• [x] New Feature (non-breaking change which adds functionality)

Related Issues

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