[Rust] Remove specialisation from Rust parquet

[asfimport]

This is a very initial attempt at removing the specialization features from the Rust Parquet implementation.

The specialisation is too complex to be covered by min_specialization and requires a bit of reworking in the crate.

Right now the code dispatches in sub-traits and methods on the Parquet type, and uses a combination of trait abuse, macros and transmutes to eliminate the feature.

I have broken this up into several commits ranging from the simplest removals (which could probably be taken fairly easily) to the most ugly and complex.

I am not stoked on the transmute abuse, and I think another take (or follow up) should be taken to remove as many as possible in the code.

The general trait for DataType::T has been made a private sealed trait to make it impossible to implement external to the Parquet crate, this is intentional as I dont think many of the public interfaces are sensible for end users to be able to implement.

TODO:

• Purge the added std::mem::transmutes if possible
• Refine and rationalise the unimplemented! implementations
• Performance test?

Reporter: Greg Bowyer / @GregBowyer
Assignee: Greg Bowyer / @GregBowyer

Related issues:

• [Rust] Support stable Rust (relates to)
• [Rust] [Parquet] Improve performance of the parquet compressors (is related to)

PRs and other links:

• GitHub Pull Request #8698

_{Note: This issue was originally created as ARROW-10636. Please see the migration documentation for further details.}

[asfimport]

Andrew Lamb / @alamb:
Related to (or perhaps a dupe) of ARROW-6717

[asfimport]

Andrew Lamb / @alamb:
Issue resolved by pull request 8698
#8698

[asfimport]

Greg Bowyer / @GregBowyer:
I am excited to see what you get, it does occur to me maybe we should run a bench on ARM, but I think at this point might be over-analyzing everything :S