gh-69093: improve sqlite3.Connection.blobopen() error handling

[erlend-aasland]

Unless sqlite3_blob_open() returns SQLITE_MISUSE, the error code and
message are available on the connection object. This means we have to
handle SQLITE_MISUSE error messages explicitly.

gh-69093

[erlend-aasland]

I noticed this comment in the sqlite3_blob_open docs:

Unless it returns SQLITE_MISUSE, this function sets the database connection error code and message accessible via sqlite3_errcode() and sqlite3_errmsg() and related functions.

_pysqlite_seterror uses the error code/message that is set on the connection object, so we need to handle the SQLITE_MISUSE case explicitly. Unfortunately (or luckily), there is no way for us to force such an error, so we cannot add a unit test for this.

[erlend-aasland]

This reminds me that we need to map SQLITE_MISUSE to InterfaceError iso. ProgrammingError. But that belongs to issue #89022.

UPDATE, see gh-91572.