Add tribal knowledge base and /executorch-kb skill (#19003) #3013

Job	Run time
test-arm / test-backend-macos	-1s
test-arm / test-backend-linux (arm_tosa_fp, models) / linux-job	30m 26s
test-arm / test-backend-linux (arm_vgf_fp, models) / linux-job	31m 20s
test-arm / test-backend-linux (arm_vgf_fp, operators) / linux-job	16m 50s
test-arm / test-backend-linux (arm_tosa_fp, operators) / linux-job	19m 10s
test-arm / package-golden-artifacts	43s
	1h 38m 28s

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