Fix discarding renamed directories in Web IDE

What does this MR do?

In the discard actions, we use renameEntry to revert a rename. Unfortunately this was not enough when the parent directory no longer exists... The proposed fix in this MR is to move our createTempEntry call from our new_dropdown/modal.vue into the renameEntry action itself so that this action is properly encapsulated.

Screenshots

Before	After
20200114_ide_discard_directory_rename_bug	20200114_ide_discard_directory_fix

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

References

• #195776 (closed)