[mle] add helper method SetLeaderData(const LeaderData &)

[abtink]

No description provided.

[size-report]

Size Report of OpenThread

Merging #10245 into main(0a4d6d3).

name	branch	text	data	bss	total
ot-cli-ftd	main	467008	856	66364	534228
	#10245	466992	856	66364	534212
	+/-	-16	0	0	-16
ot-ncp-ftd	main	435892	760	61576	498228
	#10245	435876	760	61576	498212
	+/-	-16	0	0	-16
libopenthread-ftd.a	main	236091	95	40310	276496
	#10245	236077	95	40310	276482
	+/-	-14	0	0	-14
libopenthread-cli-ftd.a	main	57533	0	8075	65608
	#10245	57533	0	8075	65608
	+/-	0	0	0	0
libopenthread-ncp-ftd.a	main	31863	0	5916	37779
	#10245	31863	0	5916	37779
	+/-	0	0	0	0
ot-cli-mtd	main	364440	760	51220	416420
	#10245	364440	760	51220	416420
	+/-	0	0	0	0
ot-ncp-mtd	main	346996	760	46448	394204
	#10245	346980	760	46448	394188
	+/-	-16	0	0	-16
libopenthread-mtd.a	main	158096	0	25182	183278
	#10245	158088	0	25182	183270
	+/-	-8	0	0	-8
libopenthread-cli-mtd.a	main	39756	0	8059	47815
	#10245	39756	0	8059	47815
	+/-	0	0	0	0
libopenthread-ncp-mtd.a	main	24743	0	5916	30659
	#10245	24743	0	5916	30659
	+/-	0	0	0	0
ot-cli-ftd-br	main	550736	864	131204	682804
	#10245	550720	864	131204	682788
	+/-	-16	0	0	-16
libopenthread-ftd-br.a	main	324481	100	105126	429707
	#10245	324467	100	105126	429693
	+/-	-14	0	0	-14
libopenthread-cli-ftd-br.a	main	71320	0	8099	79419
	#10245	71320	0	8099	79419
	+/-	0	0	0	0
ot-rcp	main	62248	564	20604	83416
	#10245	62248	564	20604	83416
	+/-	0	0	0	0
libopenthread-rcp.a	main	9542	0	5052	14594
	#10245	9542	0	5052	14594
	+/-	0	0	0	0
libopenthread-radio.a	main	18870	0	214	19084
	#10245	18870	0	214	19084
	+/-	0	0	0	0