Include base classes with LINQ generation

[twsouthwick]

This change adds support to the LINQ generator to include base classes and their members so it'll be similar to what was in the 2.x version:

• Refactor LINQ generator to use a visitor pattern
• Add SdtElement expansion
• Visit base types

Part of #1813

[github-actions]

Test Results

    70 files  ±0      70 suites  ±0   1h 7m 52s ⏱️ +31s
 2 041 tests ±0   2 038 ✅ ±0   3 💤 ±0  0 ❌ ±0 
32 418 runs  ±0  32 382 ✅ ±0  36 💤 ±0  0 ❌ ±0 

Results for commit 34e52c0. ± Comparison against base commit 4ec5720.