Feature: Tab UI improvements

[yyyair]

This PR implements some minor improvements for TabbedPane and TabComponent.

Main features:

1. Added a "Reveal In Tree" option in TabComponent's popup menu, similar to "Reveal In Explorer" in vscode and other IDEs.
2. Fixed a problem that occurs when clicking the margin between the tab and the actual TabComponent. Before the fix it won't register as a click, since the TabComponent is smaller than the tab itself (so you could hover the edge of a tab with your mouse, have it marked as "hovered", but when you right-click it nothing happened).
3. Also added a separator after the bookmark options, since it was missing.

[skylot]

Looks good.
But adding new name string for already exist action is not good.
We already have 2 different names for this action and I don't want to make it worse 🤣

# same action as your 'Reveal in tree'
menu.sync=Sync with editor

# auto select active tab node in tree
menu.alwaysSelectOpened=Always Select Opened File/Class

We need to use the same action name in all places.
Maybe Sync with editor is a bad name, because people often ask to add this feature in issues 😟
For example, name of this action in other apps:

• Select Opened File in IntelliJ
• Reveal in Explorer View in VS Code
• Link with Editor (auto select) in Eclipse
• Select in Projects and Synchronize Editor with View (auto) in NetBeans

I like Select in Tree or Reveal in Tree, but if anyone have a better name, feel free to share.

And for this PR, I removed a new string and replace it with exist menu.sync. A name change I will commit later.