Make option like cursor-style-blink-interval available for configuration

[shtirlic]

Currently interval is hardcoded, would be great to have it configurable.

const CURSOR_BLINK_INTERVAL = 600;

[rhodes-b]

#6893

also talks about changing blink interval
(also includes transition style)

[00-kat]

That discussion is mostly focused on the transition, so don't think this is a duplicate of that one.