Rename FileReader to FileOpener (#2990)

[tustvold]

Which issue does this PR close?

Closes #2990

Rationale for this change

See ticket

What changes are included in this PR?

See ticket

Are there any user-facing changes?

No, file_stream is a private module

[codecov-commenter]

Codecov Report

Merging #2991 (1cbdf10) into master (c7fa789) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2991   +/-   ##
=======================================
  Coverage   85.81%   85.81%           
=======================================
  Files         282      282           
  Lines       51531    51531           
=======================================
+ Hits        44219    44221    +2     
+ Misses       7312     7310    -2     

Impacted Files	Coverage Δ
...afusion/core/src/physical_plan/file_format/avro.rs	0.00% <ø> (ø)
...tafusion/core/src/physical_plan/file_format/csv.rs	94.47% <ø> (ø)
.../core/src/physical_plan/file_format/file_stream.rs	90.47% <ø> (ø)
...afusion/core/src/physical_plan/file_format/json.rs	93.93% <ø> (ø)
...sion/core/src/physical_plan/file_format/parquet.rs	95.46% <ø> (ø)
datafusion/expr/src/logical_plan/plan.rs	77.60% <0.00%> (+0.17%)	⬆️
datafusion/expr/src/window_frame.rs	93.27% <0.00%> (+0.84%)	⬆️

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[alamb]

Sounds like a good name change to me (assuming it really is a not a pub interface -- I did not double check).

[ursabot]

Benchmark runs are scheduled for baseline = 833f588 and contender = 193fc3b. 193fc3b is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java