# Which issue does this PR close?

- Part of #6736

# Rationale for this change

While making documentation / examples for working with `Variant` in
#7661, I found it was somewhat
awkward to make `Variant` values directly from the metadata and value.
Specifically you have to

```rust
let metadata = [0x01, 0x00, 0x00];
let value = [0x09, 0x48, 0x49];
// parse the header metadata
let metadata = VariantMetadata::try_new(&metadata).unwrap();
// and only then can you make the Variant
Variant::try_new(&metadata, &value).unwrap()
```

I would really like to be able to create `Variant `directly from
`metadata` and `value` without having to make a `VariantMetadata`
structure

# What changes are included in this PR?

This PR proposes a small change to the API so creating a Variant now
looks like:

```rust
let metadata = [0x01, 0x00, 0x00];
let value = [0x09, 0x48, 0x49];
// You can now make the Variant directly from the metadata and value
Variant::try_new(&metadata, &value).unwrap()
```


# Are there any user-facing changes?
Yes, the API for creating APIs is slightly different (and I think
better)