Add an optional adapter interface for configuring transaction behavior

[tconbeer]

pg and sqlite are autocommit right now; this could be configurable...

Would be nice to have a checkbox (in the run query bar?) if the adapter supports this for enabling/disabling auto-commit.

[tconbeer]

Follow datagrip's lead:

Show a badge Tx: Auto; click that badge to switch to Tx: Manual.

Except that those states should be loadable from the adapter. So the adapter can declare a prop (class var) like TRANSACTION_MODES: list[str] = ["Auto", "Manual"],

The default mode should be configurable in a profile, although maybe that's a detail we leave to the adapter author. In that case, maybe the right interface is something like

@property
def transaction_mode(self) -> str:
   """the name of the currently-active transaction mode"""
    ...

def toggle_transaction_mode(self) -> str:
   """Switches to the next transaction mode and returns the name of the new mode"""
   ...

this interface would also be compatible with older adapter versions, which is nice. We could just take the empty string to mean "not implemented"