win-capture: Invert destination pixels when drawing monochrome cursors

[caesay]

Issue / Motivation

Currently all monochrome cursors are always rendered all-black, meaning they are invisible on dark backgrounds (see #6794).

Description

This updates the blend mode from GS_BLEND_SRCALPHA to GS_BLEND_INVDSTCOLOR when drawing monochrome cursors, so they are visible on both light and dark backgrounds.

The following monochrome cursor rendering requirements are complete:

• [x] A pixel that is black in both the top and bottom half will always be black in the final image.
• [x] A pixel that is black in the top and white in the bottom will always be white in the final image.
• [x] A pixel that is white in the top and white in the bottom will invert (XOR) the colour underneath it.
• [x] A pixel that is white in the top and black in the bottom is a no-op.

How Has This Been Tested?

Tested on Windows 10 x64 with all of the baked-in Windows cursors. All color cursors remain unchanged, monochrome cursors (such as the I-Beam and Crosshair) are now rendered inverted instead of black. This should have no impact on any other areas of the code.

Types of changes

Bug Fix

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.

[caesay]

This potentially fixes/closes the following issues: #6794 #3129.

[caesay]

Squashed two commits together and rebased to 1a7e5babc2033200381a208d3c90e51a309178fe

[caesay]

I have made the requested changes and rebased to release/28.1.

[RytoEX]

I have made the requested changes and rebased to release/28.1.

Always rebase to master when targeting the master branch. While the branches may sometimes be in sync, this is not always the case and is never guaranteed.