feat!: extract BatchReturn to batch package, add methods & tests

[rvagg]

I started off by wanting methods on BatchReturn to roughly match what's available in Rust, then I remembered that I was going to add serialization tests for this too because it's in the NI-PoRep path, then I realised that this struct is used in multiple actors and hasn't changed form since it was introduced. In builtin-actors it's in the shared "fil_actors_runtime" package for this very reason. So this PR introduces the same thing here:

• Extract BatchReturn and FailCode into a new "batch" package
• Remove all copies, through all actor versions
• Add methods to BatchReturn: Size(), AllOk(), Codes() []exitcode.ExitCode, CodeAt(n uint64) exitcode.ExitCode
• Add tests for new methods
• Add tests for serializations

This is a breaking change because it removes types that were previously there. There are no current direct uses of this type within Lotus today (I'm in the process of introducing one though). This would be a good candidate to ship in a v0.14.0 final I think.

[BigLep]

This would be a good candidate to ship in a v0.14.0 final I think.

For now, I added a note to https://github.com/filecoin-project/lotus/issues/12109 as this being an item for the "Mainnet Upgrade Release"

[BigLep]

2024-07-11 maintainer conversation: this will get merged after the nv24 release.