Replace `GUARDED_BY` with `ABSL_GUARDED_BY` in preparation for abseil… #2866

Job	Run time
env-protect-setup	11s
authorize	2s
get-dev-image / get-image	4s
code-coverage	13m 35s
clang-tidy	22m 23s
generate-matrix	2m 53s
build-and-test (BPF opt (4.14.254), kvm, --config=qemu-bpf --compilation_mode=opt --//bazel/test_...	4m 7s
build-and-test (BPF opt (6.1.106), kvm, --config=qemu-bpf --compilation_mode=opt --//bazel/test_r...	3m 52s
build-and-test (Clang debug, nokvm, --config=clang --compilation_mode=dbg, bazel_buildables_clang...	6m 56s
build-and-test (Clang opt + UI, nokvm, --config=clang --compilation_mode=opt, bazel_buildables_cl...	10m 31s
build-and-test (GCC opt, nokvm, --config=gcc --compilation_mode=opt, bazel_buildables_gcc_opt, ba...	9m 58s
build-and-test (TSAN, nokvm, --config=tsan --compilation_mode=dbg, bazel_buildables_sanitizer, ba...	7m 15s
build-and-test (Go race detector, nokvm, --config=go_race --compilation_mode=opt, bazel_buildable...	4m 29s
build-and-test (ASAN, nokvm, --config=asan --compilation_mode=dbg, bazel_buildables_sanitizer, ba...	21m 36s
build-and-test-status	3s
	1h 47m 55s

Provide feedback