Replace all the calls to get_resource_path to the better file_path or
directly use file_open when not needed
Doing both a get_resource_path and file_open means checking twice that
the file exists.
Doing a simple path concatenation before a file_open is safe.
If given to another method (e.g. etree.parse), calling file_path is
the prefered method.
Note that get_resource_path used to return False when the file does
not exists while file_path/file_open raises a FileNotFoundException
closesodoo/odoo#135607
Related: odoo/upgrade#5187
Related: odoo/enterprise#47475
Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>