[mod] reduce memory footprint by not calling babel.Locale.parse at runtime

babel.Locale.parse loads more than 60MB in RAM.  The only purpose is to get:

    LOCALE_NAMES   - searx.data.LOCALES["LOCALE_NAMES"]
    RTL_LOCALES    - searx.data.LOCALES["RTL_LOCALES"]

This commit calls babel.Locale.parse when the translations are update from
weblate and stored in::

    searx/data/locales.json

This file can be build by::

    ./manage data.locales

By store these variables in searx.data when the translations are updated we save
round about 65MB (usually 4 worker = 260MB of RAM saved.

Suggested-by: https://github.com/searxng/searxng/discussions/2633#discussioncomment-8490494
Co-authored-by: Markus Heiser <markus.heiser@darmarit.de>

docs/dev/searxng_extra/update.rst

@@ -78,6 +78,16 @@ Scripts to update static data in :origin:`searx/data/`
 .. automodule:: searxng_extra.update.update_pygments
   :members:
 
+.. _update_locales.py:
+
+``update_locales.py``
+=====================
+
+:origin:`[source] <searxng_extra/update/update_locales.py>`
+
+.. automodule:: searxng_extra.update.update_locales
+  :members:
+
 
 ``update_wikidata_units.py``
 ============================

docs/src/searx.locales.rst

@@ -10,11 +10,6 @@ Locales
    :backlinks: entry
 
 .. automodule:: searx.locales
-  :members:
+   :members:
 
 
-SearXNG's locale codes
-======================
-
-.. automodule:: searx.sxng_locales
-  :members: