Move Smallrye JWT Build docs to a separate guide

[sberyozkin]

Fixes #20736

This PR moves smallrye-jwt-build related docs into a dedicated guide and expands it further with more details - it should be done to decouple it from the smallrye-jwt guide to make it more obvious the provided API can be used independently of MP JWT and also clean up the smallrye-jwt guide.

smallrye-jwt docs's structure has also been aligned to the the OIDC doc structure.

I'll follow up with the Quarkus guides update on the web site once this one is merged.

CC @gastaldi @stuartwdouglas

[sberyozkin]

Thanks @gastaldi will follow with a website PR now

[sberyozkin]

Thanks @geoand as well, haven't noticed it was you who merged it :-)

[geoand]

YW :)

[sberyozkin]

Proposing a backport since it is really a cleanup as opposed to a new doc guide/feature, but would not be a problem if it s not backported