Pointer sensitivity: Adjust base gain range

This CL updates the `calculateBaseGain` function to use a base gain range of [1.0, 2.5]
instead of [0.5, 1.5]. This change ensures that the pointer movement is more responsive to
changes in sensitivity.

Bug: b/384552392
Test: Manual
Flag: com.android.hardware.input.pointer_acceleration
Change-Id: I5db7b1473fd5b6869f02fc4ef7aa1458a0df6f58