fix(SFT-2741): incomplete plugin uninstall

[seandelaney]

• Queries all Submission and SpamSubmission element IDs from Craft's elements table
  • Deletes from freeform_submissions
  • Deletes from searchindex
  • Deletes from elements, which cascades to elements_sites automatically
• Drops per-form submission tables
• Cleans up demo template
  • Removes the template directory at @templates/{prefix}
  • Removes the asset directory at {webRoot}/assets/{prefix}
• Cleans up project config
  • Removes plugins.freeform (edition, licence key, schema version, all settings)
  • Removes elementSources.Solspace\Freeform\Elements\Submission
  • Removes demo template routes
  • Strips freeformForms.* and freeformSubmissions.* scope entries from all GraphQL schemas
  • Strips freeform-related permission entries from all user group permissions arrays
• Cleans up user permissions
  • Deletes all freeform-* entries from userpermissions, userpermissions_usergroups, and userpermissions_users
• Cleans up widgets
  • Deletes all dashboard widgets with a type under the Solspace\Freeform\ namespace