rework the vtable implementation embedding the vtable array directly with new strictions on methods (#22991)

**TODO**
- [x] fixes changelog
With the new option `nimPreviewVtables`, `methods` are confined in the
same module where the type of the first parameter is defined

- [x] make it opt in after CI checks its feasibility

## In the following-up PRs

- [ ] in the following PRs, refactor code into a more efficient one

- [ ] cpp needs special treatments since it cannot embed array in light
of the preceding limits: ref
https://github.com/nim-lang/Nim/pull/20977#discussion_r1035528927; we
can support cpp backends with vtable implementations later on the
comprise that uses indirect vtable access

---------

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

1 files changed, 0 insertions, 1 deletions

diff --git a/config/config.nims b/config/config.nims
index 5c9c88e8a..4b8582d9c 100644
--- a/config/config.nims
+++ b/config/config.nims
@@ -21,4 +21,3 @@ when defined(nimStrictMode):
     # future work: XDeclaredButNotUsed
 
 switch("define", "nimVersion:" & NimVersion)
-