Bump third_party/pigweed/repo from `c12c17d` to `8ffdd15` #2285

Job	Run time
Build Docker CHIP Build images - base	5m 44s
Build Docker CHIP Build images - base (-minimal)	38s
Build Docker CHIP Build images - stage 1 (-crosscompile)	1m 13s
Build Docker CHIP Build images - stage 2 (-ameba)	1m 45s
Build Docker CHIP Build images - stage 2 (-asr)	1m 0s
Build Docker CHIP Build images - stage 2 (-bouffalolab)	1h 4m 35s
Build Docker CHIP Build images - stage 2 (-doxygen)	13s
Build Docker CHIP Build images - stage 2 (-efr32)	1m 37s
Build Docker CHIP Build images - stage 2 (-esp32)	2m 10s
Build Docker CHIP Build images - stage 2 (-infineon)	1m 49s
Build Docker CHIP Build images - stage 2 (-java)	50s
Build Docker CHIP Build images - stage 2 (-nxp)	4m 49s
Build Docker CHIP Build images - stage 2 (-nxp-zephyr)	2m 30s
Build Docker CHIP Build images - stage 2 (-nrf-platform)	3m 39s
Build Docker CHIP Build images - stage 2 (-telink)	4m 6s
Build Docker CHIP Build images - stage 2 (-ti)	49s
Build Docker CHIP Build images - stage 2 (-tizen)	1m 51s
Build Docker CHIP Build images - stage 2 (-openiotsdk)	53s
Build Docker CHIP Build images - stage 3 (-android)	3m 18s
Build Docker CHIP Build images - stage 3 (-esp32-qemu)	3m 23s
Build Docker CHIP Build images - stage 3 (-tizen-qemu)	16m 15s
Build Docker CHIP Build images - vscode	0s
	2h 3m 7s

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