Move `app/assets/javascripts/integrations/integration_settings_form.js` functionality to a Vue component

Class-based patterns are discouraged at GitLab. We should investigate a strategy for removing app/assets/javascripts/integrations/integration_settings_form.js and adding necessary functionality to a Vue component.

• Move getJiraIssueTypes to Vuex action !75484 (merged)
• Move "Integration active" toggle to integration_form.vue !75838 (merged)
• Move "test settings" code from integration_settings_form.js to Vue component !76291 (merged)
• Move "save settings" code from integration_settings_form.js to Vue component !76409 (merged)

Follow-up work:

• Move Integration Settings form element from HAML to Vue
• Move "reset integration" code from Vuex to Vue component internals
• Remove VALIDATE_INTEGRATION_FORM_EVENT from integrations event hub