fix(model-datastructure): avoid stack overflows when adding many children at once

[odzhychko]

Avoid stack overflows when adding many children at once by executing reactive streams in Kotlin Flows.

• Check how getAll and putAll could be added to CPHamtNode so that no long chains of flatMap/andThen are needed in the first place.
• Check performance impact of changes.

To be verified by reviewers

• Relevant public API members have been documented
• Documentation related to this PR is complete
  • Boundary conditions are documented
  • Exceptions are documented
  • Nullability is documented if used
• Touched existing code has been extended with documentation if missing
• Code is readable
• New features and fixed bugs are covered by tests

[github-actions]

Test Results

  199 files    199 suites   34m 18s ⏱️
1 099 tests 1 087 ✅ 8 💤 4 ❌
1 109 runs  1 097 ✅ 8 💤 4 ❌

For more details on these failures, see this check.

Results for commit 8d189af.

♻️ This comment has been updated with latest results.