hterm: use display none rather than positioning to hide cursor
hterm: use display none rather than positioning to hide cursor

This CL is preparation to allow padding within x-screen.
With padding, the cursor becomes visible again when it is positioned
at (-1, -1), so it is better to set display:none.

Bug: 267654
Change-Id: I8f26e4c7f7956247ea5a30a2a82f4dd5978e7d45
Reviewed-on: https://chromium-review.googlesource.com/c/apps/libapps/+/2160614
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm