Add tribal knowledge base and /executorch-kb skill (#19003) #2968

Job	Run time
test-arm / test-backend-linux (arm_tosa_fp, operators) / linux-job	19m 32s
test-arm / test-backend-linux (arm_tosa_fp, models) / linux-job	32m 41s
test-arm / test-backend-linux (arm_vgf_fp, operators) / linux-job	16m 15s
test-arm / test-backend-linux (arm_vgf_fp, models) / linux-job	32m 1s
test-arm / test-backend-macos	-6s
test-arm / package-golden-artifacts	48s
	1h 41m 11s

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