feat: add `ape_toolchain` macro

The macro registers APE binaries for the platform contraints that are supported.

This prevents host platforms that are unsupported from resolving the toolchain.

```py
load("@ape//ape/toolchain:defs.bzl", "ape_toolchain")

toolchain_type(
    name = "type",
)

ape_toolchain(
    name = "ape",
    toolchain = "@ape//:curl",
    toolchain_type = ":type",
)
```