Added start_date and end_date to user bulk edit

[snipe]

This adds the start_date and end_date to the users' bulk edit.

[what-the-diff]

PR Summary

• Enhanced Update Method in BulkUsersController
  The update process in our Users section has seen significant improvements. The 'update' command now intelligently adds 'start_date' and 'end_date' to the appropriate array, based purely on what input values it receives.

• Text Update in General Settings
  We've made changes to the key terminology for a more intuitive user experience. The term "assets" has been replaced with "selections" in the translation set.

• Text Amendment in Bulk Hardware View
  In our hardware management view, we've echoed the terminology change made in general settings. "assets" has been refreshed to "selections" to maintain consistency.

• Added Date Fields in Users Bulk Edit View
  In our Users Bulk Edit section, we've incorporated 'start_date' and 'end_date' fields. This gives admin the ability to set these values to null when necessary. The changes also reflect our new text terminology, swapping "users" with "selections".