ENH - Compute ecliptic location of bin centers in GLOWS L2 (post-SPICE)

[maxinelasp]

Parent issue: #1276

DailyLightcurve.ecliptic_lon and ecliptic_lat are currently set to np.zeros(number_of_bins) (glows_l2_data.py:92-93).

These should be computed using SPICE: given the spin-axis ecliptic longitude/latitude (available from spin_axis_orientation_average in L1B) and the GLOWS scanning circle radius, compute the J2000 ecliptic longitude and latitude of each histogram bin center. See Section 12.7.6 of the algorithm document for context — these coordinates are also needed for the bad-angle masking in #2721.

[maxinelasp]

imap_spin_angle_bin_cntr is currently filled with zeros in L1B - this is blocked

[vmartinez-cu]

Open PR #2760 computes the imap_spin_angle_bin_cntr variable. Wait for this to merge