Pipeline Graph Structural Update: Small UI Fixes
What does this MR do?
Fixes UI bugs listed in the table.
Screenshots (strongly suggested)
| before | after | |
|---|---|---|
| fix scrolling within sub-graphs |  |
 |
| dropdown appear on top |  |
 |
| click upstream button when open |  |
 |
Does this MR meet the acceptance criteria?
Conformity
Availability and Testing
-
Review and add/update tests for this feature/bug](https://docs.gitlab.com/ee/development/testing_guide/index.html). Consider all test levels. See the Test Planning Process.
Related to #276949 (closed)