Fix: do not strip special characters from labels

[AdamoLeKing]

Description

Since commit 999e1c1, PluginFieldsToolbox::sanitizeLabel() is applied to every
label written in PluginFieldsLabelTranslation and to container labels.
It strips every character that is not a letter, digit, space, -, _ or .,
so a field labelled "N° d'inventaire / site" is displayed as "N dinventaire site".

Labels are plain data:

• stored through parameterized queries,
• escaped on output (htmlspecialchars, Twig autoescape),
• injected into generated class files only through var_export(), which is safe
  for any string.

System names (table, column, class and file names) are still restricted by
sanitizeSystemName() / getSystemNameFromLabel(), so the security fix is preserved.

Changes

• Stop calling sanitizeLabel() on labels in PluginFieldsLabelTranslation,
  PluginFieldsToolbox::prepareLabel(), PluginFieldsContainer and PluginFieldsDropdown
  (labels are only trimmed).
• name and id sanitization is unchanged.

Note

Labels already saved since 999e1c1 remain truncated in
glpi_plugin_fields_labeltranslations and glpi_plugin_fields_containers.
Field labels can be restored from glpi_plugin_fields_fields.label; a migration
could be added if maintainers want it.

[stonebuzz]

Many fix about this, please add unit test
Bestr egards