bun_core/util: delete unused ArrayLike trait (#31536)

Removes the `ArrayLike` trait, the `Of<A>` type alias, the `from()` /
`from_slice()` / `from_slice_boxed()` free functions, and the `impl
ArrayLike for Vec<T>`.

These were ported from Zig's comptime-reflection helpers as
placeholders, but every call site in the Rust port ended up using
inherent `from_slice` / `append_assume_capacity` methods on the concrete
collection types instead. Nothing in the workspace references the trait
or any of the free functions.

Verified with a full debug build (`bun bd`).