VAULT-7698 Fix ignored parameter warnings for endpoint arbitrary data options

[VioletHynes]

The changes made to TestHTTP_Wrapping made the test fail before my fix, and this fixes the issue.

The output of an unwrap no longer contains a warning:

vault write -force sys/wrapping/unwrap
Key    Value
---    -----
foo    bar

I could not find any other endpoint that would be appropriate to add TakesArbitraryInput: true to, but it made sense to me to add the new option to the framework instead of simply making an exception for this particular endpoint, which felt messy. It seems likely we'll have need for this boolean in the future.

[mpalmi]

Changes look good to me, but I'm not sure how the error [warning] came to be. What is it about seal unwrapping that causes non-field data to be populated? Just want to double-check that this behavior is not caused by some other mechanism acting up.

[VioletHynes]

Changes look good to me, but I'm not sure how the error [warning] came to be. What is it about seal unwrapping that causes non-field data to be populated? Just want to double-check that this behavior is not caused by some other mechanism acting up.

Wrapping wraps the data presented in the request. It doesn't actually have a Field object, it just literally uses data.Raw to take everything. I think it makes sense in this case - wrapping is a weird endpoint but it makes sense for it to work like this.