Uri/Authority/PathAndQuery::from_static should be const

[carlsverre]

Currently using from_static to build Uri, Authority, or PathAndQuery types can't be done in a const context. From inspecting what they do under the hood, it seems like the parsing logic would be possible to extract into a const fn. Is there some other limitation preventing these methods from being const?

My use case is building Uri components at compile time for trivial assembly at runtime.

[seanmonstar]

I don't think there's a reason, other than no one has done so yet.