Avoid code duplications in ECT face extension (BLAST-WarpX#2557)

* Refactoring the nborrow functions

* Refactoring the one cell extension

* Refactoring the eight cells extension

* Enabling 2D

* Bug fix

* Some more improvements

* Fixing templates

* Switching the order of templates and AMREX_GPU_DEVICE

* Adding the needed AMREX_GPU_DEVICE in WarpX.H

* Fixing GPU related issues

* Fixed a for loop bound

* Making the new functions free

* Suggestion from review

* Suggestion from review

Co-authored-by: Axel Huebl <[email protected]>

* Suggestion from review

Co-authored-by: Axel Huebl <[email protected]>

* Improve loops over dimensions for 2D

Co-authored-by: Axel Huebl <[email protected]>

Author: 2 people