[v1.5.1] Add rotation extension

[mcencini]

This is a draft containing the necessary changes to support rotation extension which not depend on rotate3D (#302) or set_block/get_block refactoring (#341, including gradient continuity check).

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
/home/runner/.local/lib/python3.12/site-packages/pypulseq
__init__.py	42	35	17%	18–19, 36–68
block_to_events.py	17	13	24%	19–28, 33–40
calc_duration.py	25	22	12%	27–58
calc_rf_center.py	11	7	36%	25–34
check_timing.py	96	86	10%	24–211, 232, 239, 249–293
convert.py	40	11	72%	42, 48, 66, 72–73, 80, 82, 86–89
decompress_shape.py	32	29	9%	26–70
event_lib.py	96	79	18%	6–9, 41–45, 48–51, 69–82, 105–128, 150–172, 185, 205–210, 227–230, 247, 275–315
opts.py	66	22	67%	78, 83, 89, 94, 99, 102, 105, 107, 109, 112, 114, 116, 118, 120, 122, 124, 142, 166–170
/home/runner/.local/lib/python3.12/site-packages/pypulseq/SAR
SAR_calc.py	5	2	60%	7–9
/home/runner/.local/lib/python3.12/site-packages/pypulseq/Sequence
sequence.py	645	627	3%	10–13, 26–1872
/home/runner/.local/lib/python3.12/site-packages/pypulseq/utils
tracing.py	16	7	56%	16, 33–34, 42, 54–55, 75
TOTAL	1091	940	14%

Tests	Skipped	Failures	Errors	Time
18	0 💤	0 ❌	18 🔥	3.834s ⏱️