support convert for UniStr from Vector{UInt8} #51

Job	Run time
Julia 1.6 - ubuntu-latest - x64 - push	8m 57s
Julia 1.6 - ubuntu-latest - x86 - push	7m 31s
Julia 1.6 - macOS-latest - x64 - push	8m 38s
Julia 1.6 - windows-latest - x64 - push	14m 28s
Julia 1.6 - windows-latest - x86 - push	16m 36s
Julia 1.9 - ubuntu-latest - x64 - push	5m 45s
Julia 1.9 - ubuntu-latest - x86 - push	5m 17s
Julia 1.9 - macOS-latest - x64 - push	7m 17s
Julia 1.9 - windows-latest - x64 - push	5m 47s
Julia 1.9 - windows-latest - x86 - push	7m 51s
Julia nightly - ubuntu-latest - x64 - push	3m 18s
Julia nightly - ubuntu-latest - x86 - push	4m 11s
Julia nightly - macOS-latest - x64 - push	3m 46s
Julia nightly - windows-latest - x64 - push	5m 38s
Julia nightly - windows-latest - x86 - push	7m 20s
	1h 52m 20s

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