Add support for handeling slew issues for UTE trajectories

[chaithyagr]

In #269 we updated the trajectory spec, allowing for having a buffer before switching on ADC. This allows to better handle pre-phsors and rewinders.
However, the UTE trajectories were not fully handled.
In particular, things that could be addressed:

• Add support for prephasors, re-winders with timing etc #269 (comment)
• Add support for prephasors, re-winders with timing etc #269 (comment)

[Daval-G]

You are right, and we certainly need an additional block to handle that, like #272 or #221 you mentioned