Major performance degradation introduced with 10.3.3 (UTF8 char fetch)

[pl752]

Hello, @cincuranet , I was fiddling with @fdcastel `s PR (#1203) when I have noticed that between used in his PR nuget 10.3.1 and master there was an update (10.3.3) which significantly affected performance and allocation rates when woring with UTF8 strings.

Method	Job	BuildConfiguration	DataType	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Fetch	NuGet100	10.3.2	CHAR((...) UTF8 [28]	1.007 s	0.0261 s	0.0770 s	1.01	0.11	46000.0000	7000.0000	369.79 MB	1.00
Fetch	Core100	10.3.3	CHAR((...) UTF8 [28]	2.131 s	0.0420 s	0.0810 s	2.13	0.18	543000.0000	112000.0000	4339.37 MB	11.73

Interesting fact is that the update was fixing an issue around the same place where one of my old PRs (#1252) was implementing optimizations directly related to affected methods. Related issue resulting in problematic fix bd0db88: #1213

Table relaed to my PR vs 10.3.1

Method	Job	BuildConfiguration	DataType	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Fetch	NuGet100	ReleaseNuGet	CHAR((...) UTF8 [28]	1.066 s	0.0398 s	0.1175 s	1.01	0.16	46000.0000	7000.0000	369.79 MB	1.00
Fetch	Core100	Release	CHAR((...) UTF8 [28]	1.161 s	0.0232 s	0.0683 s	1.10	0.14	46000.0000	7000.0000	369.79 MB	1.00

Can you, please, review my PR changes and check if they are correct (aka they won't reintroduce the fixed issue, tests are passing successfully meanwhile)?