SATS: Flatten AlgebraicType, getting rid of BuiltinType

[Centril]

Description of Changes

Take 2 of #379.

API and ABI breaking changes

Any API/ABI relying on AlgebraicTypes BSATN serialization will break.

Expected complexity level and risk

3, where the complexity is primarily in codegen.

[cloutiertyler]

Have you done any testing of the codegen @Centril? AFAICT the changes seem more or less minimal for what we need to do.

[Centril]

Have you done any testing of the codegen @Centril? AFAICT the changes seem more or less minimal for what we need to do.

The Rust codegen is tested in CI but the C# sdk tests seem to be broken in CI. This PR appears to slightly break the C# SDK which clockworklabs/com.clockworklabs.spacetimedbsdk#116 is meant to fix. However, I don't know how to test the combination of this and that PR locally. I'm hoping that @bfops can help me out here.

[bfops]

Have you done any testing of the codegen @Centril? AFAICT the changes seem more or less minimal for what we need to do.

The Rust codegen is tested in CI but the C# sdk tests seem to be broken in CI. This PR appears to slightly break the C# SDK which clockworklabs/spacetimedb-csharp-sdk#116 is meant to fix. However, I don't know how to test the combination of this and that PR locally. I'm hoping that @bfops can help me out here.

The easiest way to at least get the command-line tests (dotnet test) building with a different version of SpacetimeDB is to add a nuget.config file into the root of the spacetimedb-csharp-sdk repo:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <!-- Local NuGet repositories -->
    <add key="Local SpacetimeDB.BSATN.Runtime" value="${SPACETIMEDB_REPO_PATH}/crates/bindings-csharp/BSATN.Runtime/bin/Release" />
    <!-- Official NuGet.org server -->
    <add key="NuGet.org" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
</configuration>

replace ${SPACETIMEDB_REPO_PATH} with the relative or absolute path to the SpacetimeDB repo. (I have an open PR to add a helper script for generating this file)

[bfops]

Ah actually it requires a dotnet pack as well.. this new README might help.

[bfops]

(To be clear, the C# SDK tests are not a required check on PRs - they're there to effectively warn you that something downstream will be broken and will need fixing once this merges)

[bfops]

dotnet test passed for me locally in the C# SDK repo when I tested this branch alongside clockworklabs/com.clockworklabs.spacetimedbsdk#116.

[RReverser]

Minor nits, but lgtm.