Add pending stat

[giskook]

Closes #.

What does this PR do?

Reviewers

Main reviewers:

• @john
• @doe

Codeowner reviewers:

• @-Alice
• @-Bob

[zjg555543]

I think we can add a stat service and db table to save them.

1. Define a statistics table, with content stored as key-value pairs. For example, key: tx-pending, value: {x:1, b:2}. All statistical information can be written into it.
2. Implement a statistics service or use an existing one like sync/gp to write to the table.
3. Other services can read from the table.

[giskook]

I think we can add a stat service and db table to save them.

Aggree. we need a stat service to do such thing

1. Define a statistics table, with content stored as key-value pairs. For example, key: tx-pending, value: {x:1, b:2}. All statistical information can be written into it.

Once the stat service setup, we can change the db schema to key-value pairs, now the table schema is hidden by updatePendingStat