fix: adjust the cursor-type to underline for vi-operator + the color of vi-insert cursor now respects the default cursor color

[sakurawald]

Solve part of the issue: #1648

This commit contains changes:

• The color of cursor in vi-insert-mode should respect the set default cursor color.
• The cursor-type for vi-operator should be underline, e.g. the ciw command.

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It will be better, after the bug of drawing of underline and bar cursor type in sdl2 version is fixed. The underline and bar cursor tpe is drawn well in ncursrs version.

In sdl2 version:

1. The underline cursor-type will over-draw the character under caret.
2. The bar cursor-type will over-draw the character under caret in some cases, taken "LEM" string for example.