[Project] Schema Editing API

[StefanApfel-Bentley]

This Issue acts as container for all Schema Editing API related Issues

### Editing API
- [ ] https://github.com/iTwin/itwinjs-core/issues/6837
- [ ] https://github.com/iTwin/itwinjs-core/issues/6779
- [ ] https://github.com/iTwin/itwinjs-core/issues/6800
- [ ] https://github.com/iTwin/itwinjs-core/issues/6801
- [ ] https://github.com/iTwin/itwinjs-core/issues/6582
- [ ] https://github.com/iTwin/itwinjs-core/issues/6799
- [ ] https://github.com/iTwin/itwinjs-core/issues/5892
- [ ] https://github.com/iTwin/itwinjs-core/issues/5904
- [ ] https://github.com/iTwin/itwinjs-core/issues/6881
- [ ] https://github.com/iTwin/itwinjs-core/issues/6880
- [ ] https://github.com/iTwin/itwinjs-core/issues/6883
- [ ] https://github.com/iTwin/itwinjs-core/issues/6870
- [ ] https://github.com/iTwin/itwinjs-core/issues/6896

### Validating API
- [ ] https://github.com/iTwin/itwinjs-core/issues/6798
- [ ] https://github.com/iTwin/itwinjs-core/issues/6846
- [ ] https://github.com/iTwin/itwinjs-core/issues/6305
- [ ] https://github.com/iTwin/itwinjs-core/issues/6810
- [ ] https://github.com/iTwin/itwinjs-core/issues/6938
- [ ] https://github.com/iTwin/itwinjs-core/issues/6920
- [ ] https://github.com/iTwin/itwinjs-core/issues/6942