Bump third_party/pigweed/repo from `1f12d06` to `5eec847` #906

Job	Run time
Build on Darwin (clang, python_lib, simulated)	3m 24s
Build on Linux (gcc_debug)	1h 21m 1s
Build on Linux (fake, gcc_release, clang, simulated)	1h 43m 37s
Build on Linux (coverage)	17m 21s
Build on Linux (python_lib)	1m 50s
Build on Linux (python lighting-app)	1m 46s
	3h 28m 59s

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