refactor: Make pl.repeat part of the IR

[coastalwhite]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 90.69767% with 4 lines in your changes missing coverage. Please review.

Project coverage is 79.78%. Comparing base (ee9bafb) to head (66adb47).
Report is 35 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-plan/src/dsl/function_expr/mod.rs	33.33%	2 Missing ⚠️
crates/polars-core/src/frame/column/mod.rs	90.00%	1 Missing ⚠️
.../polars-python/src/lazyframe/visitor/expr_nodes.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #19152   +/-   ##
=======================================
  Coverage   79.78%   79.78%           
=======================================
  Files        1531     1532    +1     
  Lines      208449   208476   +27     
  Branches     2913     2913           
=======================================
+ Hits       166317   166341   +24     
- Misses      41581    41584    +3     
  Partials      551      551           

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