Move schemas to schema crate, rename Def to RawDefV8

[kazimuth]

Description of Changes

This is in preparation for further schema rewrites, extracted from #1448, based on #1479. There are only name changes (well, and one bindings change due to the name changes).

I've chosen aggressive, ugly names for the existing Def types. This is because soon, these types will be considered unvalidated user input, which should not be used anywhere except at the module boundary, where they are immediately validated and converted to trusted types. I want these types to stick out in code to encourage migration away from them.

API and ABI breaking changes

This is technically an API break, but the APIs involved are only used by macros, so 🤷

Expected complexity level and risk

0

[mamcx]

LGTM.

NOTE: The removal of names for sequence and such reordering break the system tables, so I think this should be marked.

[kazimuth]

Yeah, which is why I might not remove them after all, together with SQL compatibility. But this PR doesn't actually implement that, it just renames things to make future PRs easier to read.

[kazimuth]

WAIT A MINUTE. We're on ABI version 8. Should this all be renamed RawModuleDefV8? Or possibly V9, since we are about to introduce an ABI break to make this versioned?

[cloutiertyler]

Two suggestions:

1. Use v8 instead of v0
2. remove the V0 from the type and make it v8::RawTableDef instead using a rust module

I implemented these changes here: https://github.com/clockworklabs/SpacetimeDB/pull/1519/files

Pros:

• easier to rename later if necessary
• arguably cleaner in that it allows us to eventually put all handling of a particular version under a single Rust module in the future

Cons:

• harder to tell which structure is in use at a glance

Thoughts?

[mamcx]

Good question. I think if we need constant warnings then having the version in the structs is better, else if wanna clean refactorings in the module.

[kazimuth]

Yeah, we want warnings because these are now considered unvalidated user input types, and we want people to move to the new immutable + validated ModuleDef in my upcoming PR.

[cloutiertyler]

This looks good to me. I think we're going to have to coordinate merging with with @gefjon's P0

[kazimuth]

Rebased over that, this should be good to go