Optimize IndexOf lookups

[symbiogenesis]

This extension method in Core is referenced in at least 19 places.

With this change, the performance in some cases is orders of magnitude better.

https://dotnetfiddle.net/Anb4rA

[ghost]

Hey there @symbiogenesis! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[jonathanpeppers]

It looks like you wrote a manual benchmark instead of using BenchmarkDotNet.

Can you add a benchmark for this change? and add it to this PR?

https://github.com/dotnet/maui/tree/main/src/Core/tests/Benchmarks/Benchmarks

Then let us know your results before/after. Thanks!

[symbiogenesis]

Before:

Method	Mean	Error	StdDev	Gen0	Allocated
IndexOfList	5.500 ms	0.1088 ms	0.1990 ms	5093.7500	45.78 MB
IndexOfArray	5.245 ms	0.1018 ms	0.1524 ms	5093.7500	45.78 MB
IndexOfHashSet	5.820 ms	0.1139 ms	0.2595 ms	5093.7500	45.78 MB

After:

Method	Mean	Error	StdDev	Gen0	Allocated
IndexOfList	89.60 us	1.777 us	1.975 us	-	-
IndexOfArray	89.87 us	1.551 us	1.375 us	-	-
IndexOfHashSet	5,479.40 us	107.325 us	173.310 us	5093.7500	48000043 B

[jonathanpeppers]

Awesome! Thank you!

I will put this on the list for some far future blog post. 😄

[mattleibow]

/azp run

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