MOB-429 : add limit price to price triggers screen

Links (dYdX Internal Use Only)

adds new limit price switch/input
sets trigger orders limit price
adds keyboard avoiding view modifier lib
fixes trade input keyboard interaction
updates button state to disabled during "submitting"
changes presentation mode for tl/sp screen to prompt for better keyboard interaction

Desc	After
keyboard improvements for TP/SL screen, also new limit price inputs
keyboard improvements for trade screen

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] Refactoring or Technical Debt
[ ] Documentation update
[ ] Other (please describe: )