[SPARK-53316] Add Map and Struct literal types

[rafafrdz]

Summary

• Add MapLiteral<K, V> generic struct with From impl for spark::expression::Literal, mapping to LiteralType::Map
• Add StructLiteral struct with From impl for spark::expression::Literal, mapping to LiteralType::Struct
• Completes the remaining literal types from SPARK-53316

Test plan

• Unit test for Map literal (String keys, i32 values)
• Unit test for Struct literal (two-field struct with String and Integer)
• cargo build passes
• cargo clippy passes
• cargo fmt -- --check passes