Rename `pipelines_actions.vue` to `pipelines_manual_actions_dropdown.vue`

Problem Description

The name of the file app/assets/javascripts/pipelines/components/pipelines_list/pipelines_actions.vue is very ambiguous and it doesn't clarify what the component does.

This is the component:

Proposal

Rename occurrences of pipelines_actions.vue and PipelinesActionsComponent in favor of pipelines_manual_actions_dropdown.vue and PipelinesManualActionsDropdown respectively.

Original MR

The following discussion from !53223 (merged) should be addressed:

• @mrincon started a discussion:

  To follow up: This component and file should be renamed to pipelines_manual_actions_dropdown.vue.