net-snmp: add uci section to include additional conf files #20916

Job	Run time
Feeds Package Test Build / Test aarch64_generic	6m 49s
Feeds Package Test Build / Test arm_cortex-a15_neon-vfpv4	6m 48s
Feeds Package Test Build / Test arm_cortex-a9_vfpv3-d16	6m 44s
Feeds Package Test Build / Test i386_pentium-mmx	7m 31s
Feeds Package Test Build / Test mips_24kc	6m 32s
Feeds Package Test Build / Test mipsel_24kc	7m 38s
Feeds Package Test Build / Test powerpc_464fp	6m 51s
Feeds Package Test Build / Test powerpc_8548	6m 28s
Feeds Package Test Build / Test riscv64_riscv64	6m 48s
Feeds Package Test Build / Test x86_64	6m 52s
	1h 9m 1s

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