Fix CI for latest nightly

[alamb]

Which issue does this PR close?

Closes #969

Rationale for this change

CI jobs that use the nightly rust toolchain started failing
https://github.com/apache/arrow-rs/runs/4286145388?check_suite_focus=true

I think this is related to something included in the 2021-11-22 nightly release that makes the extern crate .. syntax not work anymore

What changes are included in this PR?

Remove some uses of extern crate

Are there any user-facing changes?

Small changes to examples

[codecov-commenter]

Codecov Report

Merging #970 (4726ebb) into master (b039cf4) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #970      +/-   ##
==========================================
- Coverage   82.32%   82.31%   -0.01%     
==========================================
  Files         168      168              
  Lines       48719    48719              
==========================================
- Hits        40107    40105       -2     
- Misses       8612     8614       +2     

Impacted Files	Coverage Δ
arrow/src/datatypes/schema.rs	66.93% <ø> (ø)
arrow/src/datatypes/field.rs	53.37% <0.00%> (-0.31%)	⬇️
parquet_derive/src/parquet_field.rs	65.98% <0.00%> (-0.23%)	⬇️
arrow/src/array/transform/mod.rs	85.33% <0.00%> (ø)

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