Use SQLite native representations in JSON

[roji]

Closes #30727

/cc @danmoseley

[roji]

Note that we the JSON representation for binary data is now a hexadecimal string (same as the output of the SQLite function hex; we do a server-side conversion back to blob via unhex. Note that unhex was only introduced relatively recently (version 3.41.0, released 2023-02-08).

This is now the only case where we need a server-side conversion, because the other types (e.g. date/time) really are strings in SQLite, whereas BLOB is its own separate type.

[ajcvickers]

Good stuff!

[roji]

@ajcvickers note this annoying thing... when you override a virtual test method, apparently the [InlineData] attributes on the base are still inherited; this makes it impossible to override methods when what you want is to replace the [InlineData] (which is the case here).

I hacked around it for now, we can think about it later.

[ajcvickers]

One thing you can do is add a placeholder and then mutate the value before passing it down to the base method. See public override void Can_read_write_collection_of_ASCII_string_JSON_values(object? storeType) in JsonTypesSqlServerTest. But maybe this is just as much as a hack, and is only useful in limited cases.

[roji]

Yeah... Unfortunately [MemberData] can only point to static properties/methods, otherwise that could have been virtual and overridden (xunit is really limited here). Let's revisit this later.