Enforce maxGrad/maxSlew in makeExtendedTrapezoid.m

[rmoskwa]

mr.makeExtendedTrapezoid performs no slew or amplitude check in its default (convert2arbitrary = false) branch. Shapes that exceed system.maxGrad or system.maxSlew are constructed silently. The convert2arbitrary = true branch already gets these checks via mr.makeArbitraryGrad, so the two calling modes diverge

To keep the errors consistent with convert2arbitrary, errors are in format of 'Slew rate violation (%.0f%%)' and 'Gradient amplitude violation (%.0f%%)'

Before opening this PR, I checked by running demo scripts successfully with the commit: writeTSE, writeHASTE, writeSpiral, and some others

[rmoskwa]

Hmm...I traced through the tests a bit, failures are going through addGradients/rotate/transformFOV.

The failures do stem from genuine exceeded limits from ramp overlap. The culprit seems to be mr.addGradients. The proposed mr.makeExtendedTrapezoid check catches it downstream...which is not as helpful.

While I think a check inside mr.makeExtendedTrapezoid makes sense in case a user directly calls it, errors are more likely to spawn from a lack of checks inside mr.addGradients. Curious what maintainers think!