Add support for labels sheet names and fix gender label bug (#1078)

* Add support for labels sheet names and update survey generation logic.

Fix: #1075
This will help to generate custom labels for everything that are not in the Widgets sheet.

* Fix expand_gender to handle space after 'gender' in labels and add corresponding test case.

Fix: #1076

* Refactor label generation to iterate over sheet names, reducing code duplication

* Explain expand_gender function to handle variations in spacing around the colon in gender labels.

* Refactor label generation to support multiple sheet names and improve file deletion logic.

* Refactor function names to follow snake_case convention and add tests for merged_section_translations functionality.

Author: samuel-duhaime