feat(parquet): optionally support serde of ParquetMetaData.

[youngsofun]

Rationale for this change

I want to use arrow-rs to read parquet files in a distributed way:
read metadata in master/coordinator, distributed them to diff slave/workers to read data.

What changes are included in this PR?

no additional dependency is added if feature serde = false (by default)
when it is true, ParquetMetaData derive(serde::Serialize, serde::Deserialize)

Are there any user-facing changes?

no

[tustvold]

This approach leaks a lot of internal representation information into the public API, is there a reason you can't use the thrift definitions as they have defined serialisation already?

[youngsofun]

This approach leaks a lot of internal representation information into the public API, is there a reason you can't use the thrift definitions as they have defined serialisation already?

I got your concerns, thank you. Please give me a few days to check about it.

[youngsofun]

the thrift definitions are enough for my current usage, thank you!