New method execProtocolRaw()

[gregnr]

When passing raw message data directly to PGlite via execProtocol() (through pg-gateway), pg protocol error messages end up getting thrown by PGlite which means:

• I have to re-create the protocol error message from the DatabaseError object
• We lose any other messages that PG sent back (often a ReadyForQuery message)

Ideally there would be a way to execProtocol without the wrapping logic for this kind of use case. This PR proposes an execProtocolRaw() method that simply forwards raw message data in and returns the raw message result from PG.

Alternatively, if there is a way for execProtocol to not throw the DatabaseError and/or return the full raw message in the event of an error, that should work too.

[gregnr]

@samwillis Updated location of syncToFs() and removed the mutex

[gregnr]

One more quick thought - is there any reason why we don't await #checkReady() at the beginning of execProtocol (and now also execProtocolRaw)? Should we add this?

[samwillis]

One more quick thought - is there any reason why we don't await #checkReady() at the beginning of execProtocol (and now also execProtocolRaw)? Should we add this?

execProtocol is used by the private #runQuery and #runExec methods, the intention is that these can be used inside #init during startup (#runExec is used). If we use #checkReady inside execProtocol we would be unable to use it or those private methods inside init as the database isn't marked as ready until its completion.

My thinking was that anyone dropping down to execProtocol would be ok with having to explicitly await the waitReady promise.