Problem: vim.diagnostic.Opts.VirtualLines.current_line and
vim.diagnostic.Opts.VirtualText.current_line cause redraw
on every CursorMoved event that makes the text jump
uncomfortably with rapid cursor movement.
Solution: `current_line` state is applied only on CursorHold,
while still being cleared on CursorMoved making it so that
until the cursor has stopped on a line, its diagnostic
looks like cursor is not on the line preventing flicker.
b55a868309