Feat: Normalize TableMetadata

[c-thiel]

This is a part of the TableMetadataBuilder (https://github.com/apache/iceberg-rust/pull/587).

Normalization of TableMetadata does:

• Validate the current schema is set and valid
• Validate that all refs are valid (snapshot exists)
• Validate logs are chronological
• Normalize location (remove trailing slash)
• Validate that for V1 Metadata the last_sequence_number is 0
• If the default partition spec is specified but the spec is not present in specs, add it
• If the default sort order is unsorted but the sort order is not present, add it

In Java most of the validations can be found in the constructor: https://github.com/apache/iceberg/blob/ab2c6f889d07eeee51a1f58605be248e9330d91b/core/src/main/java/org/apache/iceberg/TableMetadata.java#L265

[c-thiel]

Thank you very much for working on this. I have a few style suggestions, but please feel free to disregard them if they don't suit you.

Thanks @Xuanwo, they all make sense! Addressed in Improve readability & comments