[econstr] Continue consolidation of EConstr API under `interp`.

This commit was motivated by true spurious conversions arising in my
`to_constr` debug branch.

The changes here need careful review as the tradeoffs are subtle and
still a lot of clean up remains to be done in `vernac/*`.

We have opted for penalize [minimally] the few users coming from true
`Constr`-land, but I am sure we can tweak code in a much better way.

In particular, it is not clear if internalization should take an
`evar_map` even in the cases where it is not triggered, see the
changes under `plugins` for a good example.

Also, the new return type of `Pretyping.understand` should undergo
careful review.

We don't touch `Impargs` as it is not clear how to proceed, however,
the current type of `compute_implicits_gen` looks very suspicious as
it is called often with free evars.

Some TODOs are:

- impargs was calling whd_all, the Econstr equivalent can be either
  + Reductionops.whd_all [which does refolding and no sharing]
  + Reductionops.clos_whd_flags with all as a flag.

1 files changed, 7 insertions, 0 deletions

diff --git a/dev/ci/user-overlays/06511-ejgallego-econstr+more_fix.sh b/dev/ci/user-overlays/06511-ejgallego-econstr+more_fix.sh
new file mode 100644
index 000000000..4b681909d
--- /dev/null
+++ b/dev/ci/user-overlays/06511-ejgallego-econstr+more_fix.sh
@@ -0,0 +1,7 @@
+ if [ "$CI_PULL_REQUEST" = "6511" ] || [ "$CI_BRANCH" = "econstr+more_fix" ]; then
+    ltac2_CI_BRANCH=econstr+more_fix
+    ltac2_CI_GITURL=https://github.com/ejgallego/ltac2
+
+    Equations_CI_BRANCH=econstr+more_fix
+    Equations_CI_GITURL=https://github.com/ejgallego/Coq-Equations
+fi