Scroll Speed assumes that BPM doesn't reset SV to 1.0

[Eve-ning]

Describe the bug

Currently, we assumed that scroll_speed BPM takes on the SV of the previous SV line, which is not true.
in osu! behavior, the BPM actually forces the SV to be reset to 1.0, so implicitly the SV is reset.

For example

Normal on 200 BPM

Offset	SV	BPM	Scroll Speed
0	2	100	1.0
1		200	1.0
2	2	200	2.0

reamber incorrectly assumes that offset 1 has double scroll speed.