Improve Buffer documentation, deprecate Buffer::from_bytes add From<Bytes> and From<bytes::Bytes> impls

[alamb]

Which issue does this PR close?

• Closes Public API using private types: Buffer::from_bytes takes unexported Bytes #6754
• Follow on to Add doctest example for Buffer::from_bytes #6920 from @kylebarron
• Relate to [Parquet] Reuse buffer in ByteViewArrayDecoderPlain  #6930 from @XiangpengHao

Rationale for this change

As described by @tv42 #6754 and @kylebarron in #6930 creating Buffers in a zero copy way is confusing, I have also been personally confused by Bytes and bytes::Bytes difference

Also, the fact it is not clear how to make a Buffer in a zero copy manner lead to unintended copies as described by @XiangpengHao in

• Improve performance reading ByteViewArray from parquet by removing an implicit copy #6031

At least part of this confusion is that Bytes is an internal (non pub) struct that is named the same as bytes::Bytes but appears in the public API

I would like to make the whole situation less confusing

What changes are included in this PR?

1. Add documentation to Bytes making it clear it is internal and how it is related to bytes::Bytes
2. Improve documentation on Buffer and add examples of how to construct Buffer from Vec and bytes::Bytes
3. Add From impls to make it easier to create Buffer in zero copy manner (used in examples)
4. Deprecate from_bytes to close Public API using private types: Buffer::from_bytes takes unexported Bytes #6754
5. Update parquet reader to use new From impls
6. Misc other documentation improvements

Are there any user-facing changes?

1. Better Docs
2. From impls for Buffer