Review feedback

include/grpc/impl/codegen/grpc_types.h

src/core/lib/iomgr/executor.h

src/core/lib/iomgr/iomgr.c

src/core/lib/iomgr/iomgr.h

src/core/lib/security/credentials/jwt/jwt_verifier.c

src/core/lib/security/credentials/jwt/jwt_verifier.h

src/core/lib/slice/slice_buffer.c

src/core/lib/surface/init.c

test/core/internal_api_canaries/iomgr.c

test/core/iomgr/fd_conservation_posix_test.c

test/core/iomgr/fd_posix_test.c

test/core/iomgr/resolve_address_test.c

test/core/iomgr/udp_server_test.c

test/core/security/jwt_verifier_test.c

test/core/security/verify_jwt.c

tools/run_tests/sanity/core_banned_functions.py