Reduce bitcoin-cli dependencies
Always log number of threads for script verification

Helps for troubleshooting.
Change -genproclimit default to 1

This is less surprising.

Avoids the overload-the-CPU default of using N threads for script
verification as well as N threads for generation where N is number of cores.
Merge pull request #5221

93a6022 Reduce bitcoin-cli dependencies (Pieter Wuille)
Remove secp256k1 directory
Squashed 'src/secp256k1/' content from commit ef6f677

git-subtree-dir: src/secp256k1
git-subtree-split: ef6f677679d7c2a5ba7d3ad85da0456a1d086a3e
Merge commit '4d327b3221bbeceff8d8b1709c131d1212737639' as 'src/secp256k1'
Always build and link libsecp256k1
Do not use EC code in global constructors
Use libsecp256k1 in key.cpp
Do optional signature-s negation inside the tests
Don't use bashisms in configure
depends: add gmp package
depends: quit exporting in config.site
build: fixup configure to not export anything
build: secp256k1 as a subdir, since it's required