arrow

ARROW-8597 [Rust] Lints and readability improvements for arrow crate

+ Pedantic fixes to `unsafe`
+ Changes to function arguments to pass in references or values as appropriate
+ Refactor pointer arithmetic to use `usize` instead of `isize` casting
+ Ignore generated code clippy warnings
+ Refactor loops to use iterators where appropriate
+ Remove unnecessary `return` statements
+ Remove unnecessary `clone` statements
+ Remove unnecessary closures
+ A bunch of similar small scale refactorings

Tests below are currently failing on master locally as well with `ARROW_TEST_DATA not defined: NotPresent`, assuming that is ok for now:

```
ipc::reader::tests::read_generated_files
ipc::reader::tests::read_generated_streams
ipc::writer::tests::read_and_rewrite_generated_files
ipc::writer::tests::read_and_rewrite_generated_streams
```

Closes #7042 from durch/lints-and-readability-improvements

Lead-authored-by: Drazen Urch <drazen@urch.eu>
Co-authored-by: Neville Dipale <nevilledips@gmail.com>
Signed-off-by: Neville Dipale <nevilledips@gmail.com>