Surface locations from validation errors, improve TS interfaces

[Swolebrain]

Description of changes

• Improves wasm interfaces in accordance with Improve generated TypeScript Result types for Cedar WASM #806
• Also subsumes changes in Add source location to cedar-wasm validate result #805, which needed to be rebased

Issue #, if available

806

Checklist for requesting a review

The change in this PR is (choose one, and delete the other options):

• A backwards-compatible change requiring a minor version bump to cedar-policy (e.g., addition of a new API).

I confirm that this PR (choose one, and delete the other options):

• Does not update the CHANGELOG because my change does not significantly impact released code.

I confirm that cedar-spec (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar formal model or DRT infrastructure.

[aaronjeline]

Looks good. My only comment is on two changes:
You changed a pub enums variant name, and all the changes from untagged to tagged(type), doesn't this make this a breaking change?

[Swolebrain]

Looks good. My only comment is on two changes: You changed a pub enums variant name, and all the changes from untagged to tagged(type), doesn't this make this a breaking change?

Totally, but cedar-wasm is basically unreleased. People re using it by building directly from source, but it's not officially really released. I don't have strong opinions as to whether it's okay to do this though.

[cdisselkoen]

This conflicts with #800 which will be making more changes, but I think this PR is good on its own and we can take it and then revise #800 accordingly.

[cdisselkoen]

Heads-up: #800 does want to make breaking changes to some of the choices in this PR. Reviews of #800 are welcome and encouraged.

• Errors can have multiple source locations, at least in the fullness of time. (Cedar doesn't use this much currently, but miette supports it, and it seems like a good future-proofing measure to support it in the FFI now.) Propagate miette error info through FFI #800 proposes to rename sourceLocation to sourceLocations and make it a JSON array.
• Because there are many fields (up to 7) associated with each error in Propagate miette error info through FFI #800, Propagate miette error info through FFI #800 proposes to rename the main error message from error to message.
• Propagate miette error info through FFI #800 also introduces one more level of nesting for errors; validation errors are proposed to be { policyId: ..., error: { message: ..., sourceLocations: [...], ...}. This could be flattened, but I thought it was valuable to have a consistent structure for errors which could be mirrored on the TS side, and the contents of error in this struct (DetailedError in the Rust in Propagate miette error info through FFI #800) are used in many other places now, and there is not always a policyId associated with all of these errors (this struct is used for other kinds of errors as well, not just errors on policies). I'm open to removing the nesting if yall think the flatter structure is more important than a consistent DetailedError type.
• type: "error" renamed to type: "failure". I think this is more clear, since the "success" case can still contain policy evaluation errors. The top-level Failure is only for failures to parse or call the authorizer entirely.