feat: Added escape_regex operation to the str namespace and as a global function

[barak1412]

Fixes #19207.

[barak1412]

@orlp Just to be sure -

The code:

import polars as pl

df = pl.DataFrame({"text": ["abc", "def", None, "abc(\\w+)"]})

df.with_columns(escaped=pl.escape_regex('text'))

Should escape the 'text' literal, not the column, right?

Besides, I need to:

1. Add tests.
2. Add pl.escape_regex as function.
3. Refactor the code such that the namespace Expr will be translated to the function Expr.
4. Add to docs.

[orlp]

@barak1412 pl.escape_regex should only work on Python strings, and not interact with the expression API at all. I would suggest adding a warning/error if you try to pass in an expression into it, suggesting you to use Expr.str.escape_regex instead.

[codecov]

Codecov Report

Attention: Patch coverage is 96.87500% with 2 lines in your changes missing coverage. Please review.

Project coverage is 80.21%. Comparing base (8a76dad) to head (f2a95af).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...rates/polars-plan/src/dsl/function_expr/strings.rs	85.71%	1 Missing ⚠️
.../polars-python/src/lazyframe/visitor/expr_nodes.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19257      +/-   ##
==========================================
- Coverage   80.24%   80.21%   -0.03%     
==========================================
  Files        1523     1526       +3     
  Lines      209545   209854     +309     
  Branches     2434     2436       +2     
==========================================
+ Hits       168148   168341     +193     
- Misses      40842    40958     +116     
  Partials      555      555              

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[barak1412]

Added this function so pl.escape_regex and str.escape_regex will be coupled by same implementation.

[barak1412]

@orlp I will be glad if you can look, thanks.

[barak1412]

@orlp Should be the right fix now, thanks.

[ritchie46]

Looks great @barak1412, we only miss docs entries in the python reference guide. Then it is good to go.

[barak1412]

@ritchie46 Sure, added to the docs.

I hope I changed the right places, first time I am touching the docs.

Edit:
I think CI failures are unrelated to my changes.