Make NoExtCon fields strictwip/strict-NoExtCon

This changes every unused TTG extension constructor to be strict in
its field so that the pattern-match coverage checker is smart enough
any such constructors are unreachable in pattern matches. This lets
us remove nearly every use of `noExtCon` in the GHC API. The only
ones we cannot remove are ones underneath uses of `ghcPass`, but that
is only because GHC 8.8's and 8.10's coverage checkers weren't smart
enough to perform this kind of reasoning. GHC HEAD's coverage
checker, on the other hand, _is_ smart enough, so we guard these uses
of `noExtCon` with CPP for now.

Bumps the `haddock` submodule.

Fixes #17992.

1 files changed, 0 insertions, 0 deletions

diff --git a/utils/haddock b/utils/haddock
-Subproject 38036137bce2587c6d50756f6fab8cfafeb5a63
+Subproject 5ec817a3e41b7eaa50c74701ab2d7642df86464