Implement structs and more type checks

[edg-l]

• [x] Struct definition
• [x] Struct creation
• [x] Struct field access
• [x] Struct auto derefence: i.e if struct is behind a reference, derefence it when using a field accessor.

Also adds:

• More checks:

undeclared variables:

type mismatches in expressions:

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 72.14700% with 144 lines in your changes are missing coverage. Please review.

Project coverage is 64.26%. Comparing base (e8a530d) to head (032f125).

Files	Patch %	Lines
crates/concrete_ir/src/lowering.rs	82.50%	46 Missing :warning:
crates/concrete_check/src/lib.rs	0.00%	42 Missing :warning:
crates/concrete_ir/src/lib.rs	8.82%	31 Missing :warning:
crates/concrete_codegen_mlir/src/codegen.rs	89.88%	17 Missing :warning:
crates/concrete_driver/src/lib.rs	0.00%	7 Missing :warning:
crates/concrete_ast/src/common.rs	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #93 +/- ## ========================================== + Coverage 63.82% 64.26% +0.43% ========================================== Files 33 33 Lines 2983 3355 +372 ========================================== + Hits 1904 2156 +252 - Misses 1079 1199 +120 ```

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