Update release notes for version 1.5.

[Yury-Fridlyand]

Description

Reorganize legacy release notes and add new one for the upcoming release.

Issues Resolved

Update release notes for the upcoming release.

Check List

• [ ] New functionality includes testing.
  • [ ] All tests pass, including unit test, integration test and doctest
• [ ] New functionality has been documented.
  • [ ] New functionality has javadoc added
  • [ ] New functionality has user manual doc added
• [x] Commits are signed per the DCO using --signoff

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[Yury-Fridlyand]

Converted to draft to prevent merge - this PR should be merged right before release. Reviews are still required.