fix: enhance transaction functionality

[reugn]

Motivation

Various fixes and refactoring for transaction.

Modifications

• Employ context in the Commit and Abort methods
• Use client operation timeout
• Use atomic.Int32 for the state
• Make all state reads atomic
• Clean up and improve error messages

Verifying this change

• [ ] Make sure that the change passes the CI checks.

This change is already covered by existing tests.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API: (yes / no)
• The schema: (yes / no / don't know)
• The default values of configurations: (yes / no)
• The wire protocol: (yes / no)

Documentation

• Does this pull request introduce a new feature? (yes / no)