Guard clipping to avoid resize artifacts in tree viewer

[arunjose696]

Setting the clipping region temporarily to the textBounds was originally added (https://bugs.eclipse.org/bugs/show_bug.cgi?id=291245 comment 25) to prevent images from being overdrawn when implementting RIGHT or CENTER column alignment support in StyledCellLabelProvider. However, enabling clipping causes artifact lines during tree resizing, as a temporary workaround the clipping call is now guarded and applied only in those alignment cases to avoid issues with resizing of columns.

Steps to reproduce
Step 0:Set monitor zoom to 175

1. Set monitor zoom to 175%.
2. Launch a runtime workspace.
3. In that runtime workspace, open the Debug Configurations dialog.
4. Go to the Plug-ins tab for another runtime workspace / Eclipse application.
5. Resize the ID column in the Features view. Artifact lines appear without this workaround.

Behavior without the fix

old.mp4

Behavior with the fix

new.mp4

Additionally this issue can also be reproduced with the snippet provided in vi-eclipse/Eclipse-Platform#548 (comment)

[github-actions]

Test Results

 3 018 files  ±0   3 018 suites  ±0   2h 21m 40s ⏱️ - 1m 15s
 8 242 tests ±0   7 993 ✅  - 1  248 💤 ±0  1 ❌ +1 
23 646 runs  ±0  22 854 ✅  - 1  791 💤 ±0  1 ❌ +1 

For more details on these failures, see this check.

Results for commit 24fa5b1. ± Comparison against base commit e15e9bf.