Use element indices `particle.ei` in curvilinear search #1421

Job	Run time
py3.11 \| ubuntu \| unit tests	4m 48s
py3.12 \| ubuntu \| unit tests	5m 14s
py${{ matrix.python-version }} \| ${{ matrix.os }} \| integration tests	-1s
mypy	-1s
merge-test-artifacts	0s
	10m 0s

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