Move from Try to Either

[bblfish]

The problem with Try is that it does not make explicit the type of errors that should be expected from a function. All the code in httpSig has an upper set of exceptions to be expected, and this should be made visible. It would also work better with other cats libs.
Try was a way to get things done quickly.

[bblfish]

It can be done nicely, but it gets a bit problematic with RFC8941 code which throws
exceptions (eg on Token creation(, in order to reduce the need for flatmaps everywhere. This is certainly where canthrow experimental feature could come in useful
https://docs.scala-lang.org/scala3/reference/experimental/canthrow.html

[bblfish]

Most of the migration was done in previious commit.
But if we don't allow exceptions to be thrown for simple Token creations then it really coud make using the code a bit difficult. So the can throw stuff needs to be looked at.