Freeze strings and constants in pragmas

[tenderlove]

I'm looking in earnest at Ractor support in Rails. We need some of these constants that SQLite3 uses to be frozen so that when they're accessed via Ractors we don't get an error.

This commit just adds frozen string literals, and freezes some constants

[flavorjones]

@tenderlove LMK if you need this in a release.

[flavorjones]

Side note: the freezing idiom here is kinda gross. Is there no better way to do this, like Ractor.make_shareable or # shareable_constant_value: literal?

I read through Feature #17145: Ractor-aware Object#deep_freeze and Feature #17274: Ractor.make_shareable(obj) and I also skimmed ruby/doc/ractor.md I'm still not sure I understand how this is supposed to be done.

[tenderlove]

@tenderlove LMK if you need this in a release.

I do not. I'm working off edge here, so it's fine.

Side note: the freezing idiom here is kinda gross. Is there no better way to do this, like Ractor.make_shareable or # shareable_constant_value: literal?

I didn't want to use the Ractor constant because then the code isn't backwards compatible (or we'd have to do work to make it backwards compatible). I think the comment directive might work, but IIRC there's a problem with it (that I can't remember off the top of my head). I just recall an issue while fixing a bug in Prism (not an issue with Prism, but a problem with how the directive works in practice).

I agree we're calling freeze a bunch. Maybe we should try to figure out why the data structure is nested so much? It looks like some of these constants are truly tuples, so maybe we could use a hash. I'm not sure why the other ones are nested arrays. I'll look in to it.

[flavorjones]

I didn't want to use the Ractor constant because then the code isn't backwards compatible

@tenderlove This gem only supports Ruby >= 3.1, and as far as I can tell Ractor.make_shareable was introduced into Ruby 3.0. So I'm not worried about backwards compat if you want to use it instead of freeze.