Header-aware visitor should not immediately allocate arrays sized to the limits.

[airbreather]

Cursively/src/Cursively/CsvReaderVisitorWithUTF8HeadersBase.cs

Lines 173 to 175 in eaf568a

	_headersBuilder = ImmutableArray.CreateBuilder<string>(maxHeaderCount);
	_headerBuffer = new char[maxHeaderLength];

These immediately allocate arrays that are as big as the maximum limits requested by the caller.

The caller should be able to ask us to essentially turn off enforcement of these limits by setting the value absurdly high, without having to pay the worst-case cost every single time.

[airbreather]

We should still require val <= 0x7FEFFFFF, since bigger is completely absurd, and at least these two mainstream implementations of .NET Standard 2.0 are essentially guaranteed to fail past that point anyway, so it seems to make more sense to fail early in testing instead of when it happens in production:

CoreCLR:
https://github.com/dotnet/coreclr/blob/1d47f41f3d3d1e391818323df4378e82b95292f8/src/System.Private.CoreLib/shared/System/Array.cs#L20-L25

Classic:
https://github.com/microsoft/referencesource/blob/e0bf122d0e52a42688b92bb4be2cfd66ca3c2f07/mscorlib/system/array.cs#L619-L624