FlatBuffers: Extend quality artifacts (documentation, tests)

### Component Request /Modification Description

FlatBuffers: Extend quality artifacts
- Add architecture elements
- Add component / feature integration tests
- Add unit tests
- Extend user documentation.

### Expected Changes ot work products

- [x] Requirements
- [x] Architecture
- [ ] Safety Analysis
- [ ] Security Analysis
- [x] Detailed Design
- [x] Implementation and Testing
- [ ] all

### Impact analysis

None: Component is already introduced, issue is only about adding missing quality artifacts

### Safety or Security relevance

- [ ] none
- [x] Safety relevant
- [ ] Security relevant

### Expected required ASIL classification

ASIL_B

### Expected Implementation Version (Release)

0.9