Answer a query that fails to build in its place in the pipeline

[chrbala]

When a query throws while it is built (an undefined value, more than 65534 parameters, a serializer that throws), execute has already queued it to await an answer, but nothing of it was written. The catch then rejected the connection's current query with the new query's error and left the failed query waiting for an answer that never comes, so every later answer on the connection went to the wrong query:

await sql`select 1`
const a = sql`select pg_sleep(0.1), 1 as x`
    , b = sql`select ${ undefined }`
    , c = sql`select 3 as x`
// a rejects with UNDEFINED_VALUE, b with "Cannot set properties of
// null (setting 'columns')", c never settles, nor does any later query

This is also why sql.begin(sql => [sqlselect 1, sqlselect ${ undefined }]) never settles (#1082). On a reserved connection with the transaction pipelined (begin, insert, failing query, insert, commit), both inserts committed.

Send a query the server is sure to refuse in the failed query's place. The failed query then gets an answer of its own, every later answer stays with its query, and a transaction it was part of is aborted rather than committed without it. The failed query is rejected with its own error, as a retried query already is. It is no longer marked to be described first or as a cursor, since either would make the server's error send a Sync of its own and shift the next answer.

Fixes #1082

[chrbala]

I made a few PRs from Claude which fix some problems I was having. Can you take a look?