VirtuallyRotatedTextWithTerminator: avoid building RotatedTextWithTerminator

[antonioaversa]

Improvement: avoid building RotatedTextWithTerminator and have VirtuallyRotatedTextWithTerminator access directly to the underlying TextWithTerminator.

Currently the construction of a VirtuallyRotatedTextWithTerminator instance requires wrapping the underlying TextWithTerminator into a RotatedTextWithTerminator: c.p. the following excerpt from

MoreStructures/MoreStructures/TextWithTerminatorExtensions.cs

Line 40 in 0365e3b

new(new(text, text.Terminator, false), rotation);

    public static VirtuallyRotatedTextWithTerminator ToVirtuallyRotated(this TextWithTerminator text, int rotation) =>
        new(new(text, text.Terminator, false), rotation);

Why: on large input (strings of hundreds of MB), a RotatedTextWithTerminator instance has to be built for each "virtual rotation" of the input, i.e. as many instances of this object are created as chars in the input. This leads to a high memory usage, and possibly to OutOfMemoryException.