Use `grpc_closure`s in `grpc_timer`s

src/core/ext/client_channel/channel_connectivity.c

src/core/ext/client_channel/subchannel.c

src/core/ext/lb_policy/grpclb/grpclb.c

src/core/ext/resolver/dns/native/dns_resolver.c

src/core/lib/channel/deadline_filter.c

src/core/lib/channel/deadline_filter.h

src/core/lib/channel/handshaker.c

src/core/lib/iomgr/tcp_client_posix.c

src/core/lib/iomgr/tcp_client_uv.c

src/core/lib/iomgr/tcp_client_windows.c

src/core/lib/iomgr/timer.h

src/core/lib/iomgr/timer_generic.c

src/core/lib/iomgr/timer_generic.h

src/core/lib/iomgr/timer_uv.c

src/core/lib/iomgr/timer_uv.h

src/core/lib/surface/alarm.c

test/core/end2end/fuzzers/api_fuzzer.c

test/core/iomgr/timer_list_test.c