Previously whenever the user would use touch gestures to make selections
or scroll the terminal, IME would automatically be enabled due to the
focus change and reduce the terminal height. This isn't ideal when the
goal is just scanning through the terminal history without making any
input.

This patch keeps track of pointer and touch focus and only enables IME
when either the pointer is within the window or a tap touch sequence was
performed to give the window 'touch focus'.

The initial touch tap sequence used to enable IME is still forwarded to
the terminal as a simulated click event, since otherwise touch devices
without virtual keyboard would be forced into a confusing additional tap
to make it work. This means that virtual keyboard users will not be able
to open the virtual keyboard without creating a click event, which
should still be preferable to the status quo.

This disables the OpenGL context's robustness feature since some GPUs
that advertise robustness support do not support sufficient capabilities
for our implementation.

Closes #8713.

Since Rust 1.77, `offset_of` is available in the std.

Also apply clippy changes while at it.

Closes #8002.