Validate URIs on http and https providers

[mx-psi]

The http and https providers don't do any validation of their URIs. This means it's hard for us to explore using alternative syntax for parameters as discussed on #10121. We should check whether net/http supports IDNAs and if so use https://pkg.go.dev/golang.org/x/net/idna for validation.

I argue this should be allowed after 1.0 since the URIs were invalid before and the behavior was unspecified for them.