Remove implicit `LocaleFallbackProvider` constructors (#5183) #2063

Job	Run time
Check Credentials for jobs that need JSON credentials	1s
WASM Demo	2m 11s
bench-binsize	2m 59s
bench-memory (macos-latest)	4m 4s
bench-memory (ubuntu-latest)	3m 37s
bench-memory (windows-latest)	7m 44s
bench-perf (components/collections)	4m 34s
bench-perf (components/datetime)	4m 20s
bench-perf (components/locale)	2m 38s
bench-perf (components/locale_core)	5m 14s
bench-perf (components/plurals)	6m 2s
bench-perf (components/segmenter)	3m 40s
bench-perf (provider/blob)	3m 19s
bench-perf (utils/fixed_decimal)	6m 10s
bench-perf (utils/litemap)	2m 5s
bench-perf (utils/tinystr)	6m 31s
bench-perf (utils/writeable)	3m 42s
bench-perf (utils/zerotrie)	5m 43s
bench-perf (utils/zerovec)	8m 33s
C++ docs	1m 38s
Dart docs	1m 21s
TypeScript docs	43s
Rust docs	4m 46s
Deploy to GitHub Pages	17m 5s
	1h 48m 40s

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