[FIX] base_import: wrong date format

Current behaviour:
Wrong format used when importing dates

Steps to reproduce:
1. Change your language to German
2. Go to Sales > Orders
3. Export to XLSX
4. Change to dates to german format (ie: 10.09.2023)
5. Favorites > import records > Upload file
6. Click on Test
7. "does not match format '%Y-%m-%d'"

Cause of the issue:
Only default formats were taken into account
because options are empty.

opw-3540715

closes odoo/odoo#146744

X-original-commit: bdc006a81f83efddd693a8d4f4ffaec92da36f4a
Signed-off-by: Rémy Voet (ryv) <ryv@odoo.com>

addons/base_import/models/base_import.py

@@ -560,6 +560,9 @@ class Import(models.TransientModel):
                 val = self._remove_currency_symbol(val)
                 if val:
                     if options.get('float_thousand_separator') and options.get('float_decimal_separator'):
+                        if options['float_decimal_separator'] == '.' and val.count('.') > 1:
+                            # This is not a float so exit this try
+                            float('a')
                         val = val.replace(options['float_thousand_separator'], '').replace(options['float_decimal_separator'], '.')
                     # We are now sure that this is a float, but we still need to find the
                     # thousand and decimal separator
@@ -1528,7 +1531,7 @@ class Import(models.TransientModel):
 
         return input_file_data
 
-_SEPARATORS = [' ', '/', '-', '']
+_SEPARATORS = [' ', '/', '-', '.', '']
 _PATTERN_BASELINE = [
     ('%m', '%d', '%Y'),
     ('%d', '%m', '%Y'),