Replace ic_electrode with icephys_electrode on NWBFile

[oruebel]

Motivation

Fix #1181 . replace the use of ic prefix as it has an ambigious meaning in the icephys domain. Use the prefix icephys instead

Specifically, this PR:

• Deprecate NWBFile.init(ic_electrodes ...) in favor of icephys_electrodes
• Deprecate NWBFile.ic_electrodes property in favor of NWBFile.icephys_electrodes
• Deprecate NWBFile.get/add/create_ic_electrode functions in favor NWBFile.get/add/create_icephys_electrode
• Update tests to use the new functions
• Add tests to check that the deprecation warnings are raised
• Update icephys tutorial to use icephys_electrode instead of ic_electrode

Checklist

• Have you checked our Contributing document?
• Have you ensured the PR description clearly describes problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using #XXX notation where XXX is the issue number?

[codecov]

Codecov Report

Merging #1200 into dev will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev    #1200   +/-   ##
=======================================
  Coverage   68.22%   68.22%           
=======================================
  Files          37       37           
  Lines        2316     2316           
  Branches      405      405           
=======================================
  Hits         1580     1580           
  Misses        667      667           
  Partials       69       69

Impacted Files	Coverage Δ
src/pynwb/file.py	73.99% <ø> (ø)	⬆️

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[t-b]

Fantastic!

[oruebel]

@rly this should be good to go now