Migrate the following tests to `insta`

[jsai28]

In #15178, @blaginin outlined a few areas where insta snapshots should replace the use of pre-defined strings. There's a few other files where snapshot tests need to be added that are not included in the original epic. Here are files that still use pre-defined strings for comparison tests:

• datafusion/common/src/scalar/mod.rs
• datafusion/core/src/execution/context/csv.rs
• datafusion/core/src/execution/context/mod.rs
• datafusion/core/tests/catalog/memory.rs
• datafusion/core/tests/parquet/custom_reader.rs
• datafusion/core/tests/parquet/schema_coercion.rs
• datafusion/core/tests/parquet/schema.rs
• datafusion/core/tests/sql/aggregates.rs
• datafusion/core/tests/sql/path_partition.rs
• datafusion/core/tests/sql/select.rs
• datafusion-cli/src/main.rs
• datafusion/physical-optimizer/src/pruning.rs

Most of these files contain 1-3 tests that need to be updated so I don't think it needs to be split into further pieces.

[blaginin]

Thanks, added to the list 🌻

[jsai28]

take