Blazor API Review: IUriHelper (#12425)

* Rename IUriHelper -> NavigationManager

- Remove IUriHelper interface
- Rename to NavigationManager
- Remove all traces of old naming

There's no functional or design change in this commit - just removing
all traces of the old name. The next few iterations will try to improve
the design.

* Minor API tweaks to NavigationManager

Making Initialize protected causes problems because right now the
server-side code needs to deal with one of two different
implementations, hence an exchange type is used. I followed the same
pattern that was used for auth for symmetry but I have some *cool*
thoughts.

- We can remove this when we remove stateful prerendering
- I have another idea to banish this pattern to the land of wind and
ghosts

If this ends up sticking around longer than a week in the code, lets
discuss other ideas and try to improve the pattern.

* Use hub method for server-side navigation

* Get rid of async local

* Add hub method test

* Misc bikeshedding

* Update src/Components/Server/src/Circuits/DefaultCircuitFactory.cs

Co-Authored-By: campersau <buchholz.bastian@googlemail.com>

* PR feedback