BUG: de2 vefi data has multiple epochs

[jklenzing]

Description

The combined E-field and B-field data has multiple indices, because they are offset by 0.005 s rather than on the same index.

To Reproduce this bug:

import pysat
vefi = pysat.Instrument('de2', 'vefi')
vefi.load(1983, 1)

will load data as expected. Loading data for 1983, 2 will fail.

Test configuration

• OS: Monterrey
• Version python 3.10.9
• pysat develop

Additional context

Discovered with the new test_load_with_pad tests in pysat develop

[jklenzing]

Route forward:

• [x] Deprecate '' tag
• [x] Drop efield dimension for de2_vefi tag=''
• [x] Create new de2_vefimagb instrument