feat: add CA derivation FFI bindings (validPathInfoCA, getDerivationOutputIds, queryRealisation) - #670

ca-derivations is receiving some stabilizing love now.

The following two bindings will affect the FFI bindings you're adding, so if it's not too much of a burden, I would prefer to only implement the new interface.

NixOS/nix#15322 / DrvOutput uses StorePath instead of hash modulo

This is already merged and breaks two functions:

• getDerivationOutputIds: Constructs DrvOutput{hash, outputName} using hashes from hashDerivationModulo(). After this PR, DrvOutput takes a StorePath, not a Hash. The constructor, to_string(), and the overall approach need to be reworked.

• queryRealisation: Calls DrvOutput::parse(id). The signature changed to DrvOutput::parse(const StoreDirConfig&, std::string_view), so this won't compile.

NixOS/nix#15289 / Remove "deep realisations"

I expect this to be merged soon. It tracks dependencies better, avoiding some frankenbuild problems.
Here it will additionally break:

• *queryRealisation: Iterates over real->dependentRealisations, which is removed. The Haskell return type includes dependent realisations as a Map ByteString ByteString`; that part of the API would need to be dropped.

• Semantic change: deep realisations (keyed on unresolved drv paths) are no longer stored. Callers that query with an unresolved derivation's DrvOutput will always get Nothing. They would need to resolve the derivation first.