csv allow only header and fix lazy rename

[ritchie46]

fixes #3384
fixes #3361

[codecov-commenter]

Codecov Report

Merging #3423 (20173b6) into master (7911011) will decrease coverage by 0.00%.
The diff coverage is 20.83%.

❗ Current head 20173b6 differs from pull request most recent head 1301215. Consider uploading reports for the commit 1301215 to get more accurate results

@@            Coverage Diff             @@
##           master    #3423      +/-   ##
==========================================
- Coverage   61.59%   61.59%   -0.01%     
==========================================
  Files         396      396              
  Lines       68573    68592      +19     
==========================================
+ Hits        42238    42248      +10     
- Misses      26335    26344       +9     

Impacted Files	Coverage Δ
polars/polars-io/src/csv_core/utils.rs	70.57% <0.00%> (-3.00%)	⬇️
polars/polars-io/src/csv_core/parser.rs	81.53% <71.42%> (-0.17%)	⬇️
...olars/polars-core/src/frame/groupby/into_groups.rs	48.35% <0.00%> (-0.74%)	⬇️
polars/polars-io/src/csv_core/buffer.rs	78.47% <0.00%> (+0.26%)	⬆️
polars/polars-core/src/frame/asof_join/groups.rs	77.02% <0.00%> (+0.51%)	⬆️
...ars/polars-core/src/chunked_array/ops/any_value.rs	69.91% <0.00%> (+0.88%)	⬆️
polars/polars-core/src/vector_hasher.rs	71.23% <0.00%> (+1.61%)	⬆️

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