[clang] [llvm] [AVR] Add many new AVR MCU model definitions (PR #144229)

[Tom Vijlbrief via llvm-commits]

tomtor wrote:

In the CI check I find one ` FAIL:`

```
2025-06-15T07:21:48.1250696Z FAIL: Flang :: Semantics/modfile76.F90 (3383 of 3529)
2025-06-15T07:21:48.1251772Z ******************** TEST 'Flang :: Semantics/modfile76.F90' FAILED ********************
```

but this is unrelated? (Flang, fortran)

https://github.com/llvm/llvm-project/pull/144229