fix(simple-combo): preserved the input value when selectionChanging is canceled

[georgianastasov]

Closes #14310

Additional information (check all that apply):

• [x] Bug fix
• [ ] New functionality
• [ ] Documentation
• [ ] Demos
• [ ] CI/CD

Checklist:

• [x] All relevant tags have been applied to this PR
• [x] This PR includes unit tests covering all the new code (test guidelines)
• [ ] This PR includes API docs for newly added methods/properties (api docs guidelines)
• [ ] This PR includes feature/README.MD updates for the feature docs
• [ ] This PR includes general feature table updates in the root README.MD
• [ ] This PR includes CHANGELOG.MD updates for newly added functionality
• [ ] This PR contains breaking changes
• [ ] This PR includes ng update migrations for the breaking changes (migrations guidelines)
• [ ] This PR includes behavioral changes and the feature specification has been updated with them

[georgianastasov]

🔧 Please note that at the moment this pull request will not function correctly and tests will fail. This is because the following pull requests for this issue must be merged first for compatibility:

• #14308

This PR are crucial as it provide necessary changes that this PR relies on. Once it is merged, this PR can be re-evaluated for functionality and tests can be expected to pass as intended.