a02f3f19f52e628248f81acc2410e67f3d49baf5 tidy: use misc-unused-using-decls (fanquake)
d6787bc19b1032d3f46a60625105f30199c41b00 refactor: remove unused using directives (fanquake)
3617634324d647956c621db407db6d82a91b91ec validation: remove unused using directives (eugene)
Pull request description:
Adds https://clang.llvm.org/extra/clang-tidy/checks/misc/unused-using-decls.html to our clang-tidy.
PR'd after the discussion in #25433 (which it includes).
ACKs for top commit:
jamesob:
Github ACK a02f3f19f5
Tree-SHA512: 2bb937c1cc90006e69054458d845fb54f287567f4309c773a3fc859f260558c32ff51fc1c2ce9b43207426f3547e7ce226c87186103d741d5efcca19cd355253