MNMG Egonet

[ChuckHastings]

Update Egonet to support MNMG by using MNMG BFS and MNMG induced subgraph

Steps include:

• [x] Python implementation
• [x] Define PLC (pylibcugraph) API
• [x] Define C API
• [x] Define C++ API
• [x] Implement algorithm
• [x] Define C++ unit tests
• [x] Define C unit tests
• [x] Define Python unit tests
• [x] Delete legacy implementation

### Steps
- [ ] #2873
- [ ] #2906 
- [ ] #2907 
- [ ] #2908 
- [ ] #2909 
- [ ] #2910 
- [ ] #2911 
- [ ] #2912