* fix branch names in gitmodules that were pointing to non-existant
branches (allows running `git submodule update --remote` to find
out-of-date submodules)
* make sure commits from canonical branches are used for submodules
* "small" library bumps that deal with small correctness issues, memory
leaks, threading fixes and other general performance/bugfixing
* metrics: make it work better with multithreading, which makes
debugging easier
* stew: more compile-time support and an assortment of other fixes
* taskpools: block invalid use of GC types at compile time
* nimcrypto: accelerated sha2
* upraises: remove submodule
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