Fix song select potentially displaying BPM range with equal min/max values

[frenzibyte]

• Closes Beatmap's BPM range is shown in the carousel even if its values are rounded to the same integer #18342

The wedge determines whether to display a range or a singular value using Precision.AlmostEquals(..., 0.001f), which isn't correct given that the BPMs are rounded and can be equal in integral form but different in decimals.

Therefore the BPMs are rounded first, then casted to integers and compared to each other.

While at it, I've also included a change that avoids cases like 120 BPM formed by 120 - 120.4 turn into 180-181 BPM when DT is enabled, instead of staying singular at 180 BPM.

However, that... involved rounding twice to achieve expectations, first rounding the decimal BPM value to integral (e.g. 120.6 -> 121), then rounding the rounded BPM with the decimal rate applied to it (e.g. 121 * 1.5 -> 181.5 -> 182).

Can consider reverting if the rate should be applied to the decimal BPM directly and let cases like the one mentioned above (120 -> 180-181) to remain as-is.