Deprecate TypedListener for removal to make it strongly internal later

[HannesWell]

The class TypedListener is intended to be internal even if it's in a public package and because there were cases where it has to be used for custom widges it happened that it was still used. With the APIs introduced in #1112 there are better solutions using only public APIs for the cases it was still used.

Together with #1615 this is the continuation of #1101 (comment) to deprecate TypedListener for removal so that it can later be moved into an internal package to strengthen the statement that it's internal.

Eclipse Nebula also does not use

• Rework SplitButton to not use SWT's internal TypedListener EclipseNebula/nebula#582
• Replace usage of internal SWT TypedListener and SWTEventListener EclipseNebula/nebula#583
• Use Widget.removeTypedListener() in CheckTableCombo EclipseNebula/nebula#602
• Replace usage of internal SWT TypedListener in CheckTableCombo EclipseNebula/nebula#613

[github-actions]

Test Results

   483 files  ±0     483 suites  ±0   8m 26s ⏱️ - 4m 8s
 4 095 tests ±0   4 085 ✅ ±0   7 💤 ±0  3 ❌ ±0 
16 173 runs  ±0  16 080 ✅ ±0  90 💤 ±0  3 ❌ ±0 

For more details on these failures, see this check.

Results for commit e7dec2f. ± Comparison against base commit e6588c2.