Remove unsafe code and make scheme parsing faster in Uri

[MihaZupan]

The previous logic had two similar helpers to match strings to schemes (CheckKnownSchemes and CheckSchemeSyntax). CheckKnownSchemes was only used on 32-bit targets, and CheckSchemeSyntax wasn't checking half of the known schemes.

I merged the two helpers into one while removing the unsafe code and recognizing all known schemes on all platforms.
I also changed ParseSchemeCheckImplicitFile to work on a string instead of pointers since the unsafeness wasn't buying us anything. The net result is safer, faster, and fewer LOC.

Method	Toolchain	uriString	Mean	Ratio	Allocated	Alloc Ratio
Parse	main	https://a	58.63 ns	1.00	56 B	1.00
Parse	pr	https://a	46.50 ns	0.79	56 B	1.00
Parse	main	telnet://a	96.12 ns	1.00	96 B	1.00
Parse	pr	telnet://a	60.24 ns	0.63	56 B	0.58
Parse	main	wss://a	54.88 ns	1.00	56 B	1.00
Parse	pr	wss://a	53.77 ns	0.98	56 B	1.00

(not needed for 8.0)

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Issue Details

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The previous logic had two similar helpers to match strings to schemes (CheckKnownSchemes and CheckSchemeSyntax). CheckKnownSchemes was only used on 32-bit targets, and CheckSchemeSyntax wasn't checking half of the known schemes.

I merged the two helpers into one while removing the unsafe code and recognizing all known schemes on all platforms.
I also changed ParseSchemeCheckImplicitFile to work on a string instead of pointers since the unsafeness wasn't buying us anything. The net result is safer, faster, and fewer LOC.

Method	Toolchain	uriString	Mean	Ratio	Allocated	Alloc Ratio
Parse	main	https://a	58.63 ns	1.00	56 B	1.00
Parse	pr	https://a	46.50 ns	0.79	56 B	1.00
Parse	main	telnet://a	96.12 ns	1.00	96 B	1.00
Parse	pr	telnet://a	60.24 ns	0.63	56 B	0.58
Parse	main	wss://a	54.88 ns	1.00	56 B	1.00
Parse	pr	wss://a	53.77 ns	0.98	56 B	1.00

(not needed for 8.0)

Author:	MihaZupan
Assignees:	MihaZupan
Labels:	area-System.Net
Milestone:	-

[EgorBo]

Nice example when a cleaner and safer code is faster 👍