glue: add GlueCheckpointDB and remove external TiDB usage

[lance6716]

What problem does this PR solve?

complete glue to enable integrated into TiDB

What is changed and how it works?

• add a glue implemented CheckpointDB, which is not elegant since it repeated many MySQLCheckpointDB code. Will refine later or in this PR.

• resome some usage of TiDBManager. now NewTiDBManager is only called in tidb-lightning-ctl

• remove usage of TiDB status port through TLS. now TLS is used only supposed to connect PD/TiKV

Check List

Tests

• pass original test

Side effects

• Increased code complexity

Related changes

[lance6716]

will reduce commit message

[kennytm]

You could just git commit --amend and then git push --force, no need to create a new PR.

[lance6716]

You could just git commit --amend and then git push --force, no need to create a new PR.

Oh I should refresh this page. I force pushed and saw old commits still here 😂