Update information and button text for deployment footer

What does this MR do?

This MR updates the text and button text for the deployment footer to match the table shown in #25351 (closed). This involves also refactoring the deployment tests, as they were predicated on a certain file setup and failed when components were extracted. The main changes are:

• Adding isManual, isCurrent, canBeManuallyDeployed, and computedDeploymentStatus to app/assets/javascripts/vue_merge_request_widget/components/deployment/deployment.vue

• Refactoring the deployment.vue file to remove the code abstracted in app/assets/javascripts/vue_merge_request_widget/components/deployment/deployment_info.vue, app/assets/javascripts/vue_merge_request_widget/components/deployment/deployment_stop_button.vue, and app/assets/javascripts/vue_merge_request_widget/components/deployment/deployment_view_button.vue

• Placing deployment and its subcomponents into a separate directory

• Adding constants for the deplpyment statuses app/assets/javascripts/vue_merge_request_widget/components/deployment/constants.js and using them in test files: ee/spec/javascripts/vue_mr_widget/ee_mr_widget_options_spec.js, spec/frontend/vue_mr_widget/deployment/deployment_mock_data.js, and spec/javascripts/vue_mr_widget/mr_widget_options_spec.js

It is the first step in addressing #25351 (closed). The second will be to add in the manual deploy and re-deploy buttons.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers