ARROW-10269: [Rust] Update to 2020-11-14 nightly

[nevi-me]

This takes us from 2020-04-22 to 2020-11-14.
There have been a lot of clippy lints introduced since April, and an incompleteness feature warning about specialization (which causes CI to fail).

I have allowed almost all clippy lints in datafusion, as we have >150 warnings there.
I have made changes to fix arrow and parquet lints where I perceive them not to affect open PRs.

[nevi-me]

FYI @vertexclique

[github-actions]

https://issues.apache.org/jira/browse/ARROW-10269

[jorgecarleitao]

Segfault on the coverage, outch :/

[nevi-me]

Segfault on the coverage, outch :/

I want to look at whether we can use the new llvm-based coverage instead of tarpaulin

[nevi-me]

Segfault on the coverage, outch :/

Found and fixed the problem. We were using an older cached version of cargo-tarpaulin, but the latest version has a bug; so I've forced us into using an older version, and left a reference to the GH issue.

We should be good to go @jorgecarleitao

[codecov-io]

Codecov Report

Merging #8666 (c094456) into master (3e72c70) will decrease coverage by 0.29%.
The diff coverage is 89.07%.

@@ Coverage Diff @@## master #8666 +/- ##
==========================================
- Coverage 84.84% 84.55% -0.30% 
==========================================
Files 165 177 +12 Lines 43322 43567 +245 ==========================================
+ Hits 36757 36838 +81 - Misses 6565 6729 +164 

Impacted Files	Coverage Δ
rust/arrow/src/array/array.rs	91.48% <ø> (-0.23%)	⬇️
rust/arrow/src/compute/kernels/comparison.rs	95.89% <ø> (+0.92%)	⬆️
rust/arrow/src/error.rs	5.26% <0.00%> (-0.30%)	⬇️
rust/datafusion/src/logical_plan/expr.rs	78.94% <ø> (ø)
rust/datafusion/src/logical_plan/extension.rs	0.00% <ø> (ø)
rust/datafusion/src/logical_plan/plan.rs	83.27% <ø> (ø)
rust/datafusion/src/optimizer/filter_push_down.rs	95.95% <ø> (-2.28%)	⬇️
...ust/datafusion/src/physical_plan/hash_aggregate.rs	89.40% <ø> (+3.64%)	⬆️
rust/datafusion/src/physical_plan/merge.rs	64.51% <ø> (-2.76%)	⬇️
rust/datafusion/src/test/mod.rs	89.65% <ø> (+3.82%)	⬆️
... and 166 more

---

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[jorgecarleitao]

LGTM. Thanks a lot @nevi-me , cool fixes to the code also.

[vertexclique]

Thanks for this Neville!

[jorgecarleitao]

Do we wait for some of the PRs to be flushed, or do we merge this?

[nevi-me]

I don't see this being a big risk to open PRs (as some already have merge conflicts). We run 36 CI jobs for this, vs the normal 8; so maybe there's an efficiency argument in merging this sooner, instead of having to rebase later (which I don't mind doing).

[alamb]

🎉 -- thank you @nevi-me

FYI I filed https://issues.apache.org/jira/browse/ARROW-10597 to track enablign clippy lints in datafusion

[nevi-me]

@alamb thanks. A quick solution for many of the lints, is to run clippy-fix with -Z unstable-options, so that one doesn't manually fix them.

[alamb]

@nevi-me check it out: #8687 -- which I think enables clippy lint in all parts of the project