Rename old POWER and ENERGY metric members

We still keep the old names but we mark them as deprecated.

We need to disable the max line check in flake8 for the whole file
because the symbol names are too long, and we can't use per-line
overrides because this happens inside a docstring.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

pyproject.toml

@@ -131,6 +131,10 @@ check-yield-types = false
 arg-type-hints-in-docstring = false
 arg-type-hints-in-signature = true
 allow-init-docstring = true
+per-file-ignores = [
+  # Ignore the max-line-length (E501) because enum values are just too long
+  "src/frequenz/client/microgrid/metrics/_metric.py:E501",
+]
 
 [tool.pylint.similarities]
 ignore-comments = ['yes']