Specify and test that 0x is case-invariant in the Convert class

[Dubzer]

Hi!
I was confused by the comment, so decided to specify that method can accept 0x and 0X as a prefix for hex numbers

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[danmoseley]

Are there tests for all these already

[tannergooding]

This is already covered in the official docs under the remarks section: https://learn.microsoft.com/en-us/dotnet/api/system.convert.tobyte?view=net-8.0#system-convert-tobyte(system-string-system-int32)

Are there tests for all these already

Looks like no, @Dubzer would you mind adding explicit coverage to the various Convert.To*.cs files, specifically under the FromStringWithBase tests in https://github.com/dotnet/runtime/blob/main/src/libraries/System.Runtime/tests/System.Runtime.Extensions.Tests/System ?

[Dubzer]

@tannergooding sure! I'll add it to my PR when I have time

[Dubzer]

@tannergooding done! I've added tests and also fixed small comment typo for the ToString method