ICU sharding.

[ilonatommy]

Changes from #104 without producing dictionary and .props.
We are adding new ICU .dat files along with old ones if EnableSharding=True. Once old ICU files will not be needed anymore, they can be removed completely.

Comparison of old ICU shards with the shards produced by this PR.

New shards and libs	Size [kB]	Old shards and libs	Size [kB]
libicudata.a	1	libicudata.a	1
libicui18n.a	4216	libicui18n.a	4216
libicuuc.a	2489	libicuuc.a	2489
icudt.dat	1468	icudt.dat	1468
icudt_CJK.dat	934	icudt_CJK.dat	934
icudt_EFIGS.dat	536	icudt_EFIGS.dat	536
icudt_no_CJK.dat	1046	icudt_no_CJK.dat	1046
icudt_base.dat	1468	-	-
cudt_cjk_coll.dat	12724	-	-
icudt_cjk_full.dat	1140	-	-
icudt_cjk_locales.dat	12821	-	-
icudt_cjk_zones.dat	12790	-	-
icudt_currency.dat	17985	-	-
icudt_efigs_coll.dat	11604	-	-
icudt_efigs_full.dat	757	-	-
icudt_efigs_locales.dat	11699	-	-
icudt_efigs_zones.dat	11673	-	-
icudt_full_coll.dat	19212	-	-
icudt_full_full.dat	1677	-	-
icudt_full_locales.dat	19251	-	-
icudt_full_zones.dat	19276	-	-
icudt_normalization.dat	19762	-	-
icudt_no_cjk_coll.dat	17442	-	-
icudt_no_cjk_full.dat	1268	-	-
icudt_no_cjk_locales.dat	17484	-	-
icudt_no_cjk_zones.dat	17506	-	-

[lewing]

@akoeplinger @directhex can you help @ilonatommy fix the pipelines so that they run on a supported host?

[directhex]

@lewing needs a merge but should be fine now