Drop 'construct' prefix from tableau function names, remove exports

Rename all tableau functions in OrdinaryDiffEqExplicitTableaus and
OrdinaryDiffEqImplicitTableaus to drop the 'construct' prefix
(e.g., constructDormandPrince -> DormandPrince). Functions are no
longer exported — access via qualified names
(e.g., OrdinaryDiffEqExplicitTableaus.DormandPrince()).

Update OrdinaryDiffEqRKIP to use Verner6 instead of constructVerner6.
Update all tests to use qualified access.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ChrisRackauckas