string.IndexOf returns an incorrect value in some cases when comparisonType is `StringComparison.OrdinalIgnoreCase`

[prozolic]

Description

In string.IndexOf, when comparisonType is StringComparison.OrdinalIgnoreCase and startIndex + count causes an integer overflow, an ArgumentOutOfRangeException is not thrown. Instead, it returns an incorrect value.
If comparisonType is anything other than StringComparison.OrdinalIgnoreCase, ArgumentOutOfRangeException　is is thrown.

Reproduction Steps

// comparisonType is StringComparison.OrdinalIgnoreCase
var result = "Hello".IndexOf('o', 1, int.MaxValue, StringComparison.OrdinalIgnoreCase); // return 4 (should throw ArgumentOutOfRangeException)

// comparisonType is StringComparison.Ordinal
var result = "Hello".IndexOf('o', 1, int.MaxValue, StringComparison.Ordinal); // throw ArgumentOutOfRangeException

Expected behavior

ArgumentOutOfRangeException is thrown.

Actual behavior

incorrect value is returned.

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

This is an edge case, I have submitted a #128191

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