feat(rust, python): Add null_on_oob parameter to expr.list.get

[JamesCE2001]

Addresses first part of #15240 (first time contributing so I figured I'd add 1 and get feedback before embarking on the rest, especially as they don't seem to overlap as much as I'd expected.)

For now leaves the default behavior to null_on_oob=True (see discussion below; we will revisit the default behavior for once it has been implemented for all functions in #15240).

[codecov]

Codecov Report

Attention: Patch coverage is 86.04651% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 81.14%. Comparing base (39b486e) to head (8004174).
Report is 42 commits behind head on main.

Files	Patch %	Lines
crates/polars-plan/src/dsl/function_expr/list.rs	80.00%	3 Missing ⚠️
crates/polars-plan/src/dsl/list.rs	50.00%	2 Missing ⚠️
crates/polars-sql/src/functions.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15395      +/-   ##
==========================================
- Coverage   81.37%   81.14%   -0.24%     
==========================================
  Files        1363     1361       -2     
  Lines      176803   174683    -2120     
  Branches     2531     2531              
==========================================
- Hits       143869   141738    -2131     
- Misses      32449    32459      +10     
- Partials      485      486       +1     

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[reswqa]

It looks like we changed the default behavior of list.get, this should be a breaking change. What I wish was that we had an explicit discussion of the default value for null_on_oob in #15240 first.

[ritchie46]

It looks like we changed the default behavior of list.get, this should be a breaking change

Yes, we shouldn't change the default behaviour yet. We can do that after all operations in #15240 f are supported and we go to 1.0.

[ritchie46]

@JamesCE2001 can you default to null_on_oob = True. We can make these consistent later.

[JamesCE2001]

@JamesCE2001 can you default to null_on_oob = True. We can make these consistent later.

Done, apologies for jumping the gun. Updated original PR comment to reflect.

[ritchie46]

Looks good @JamesCE2001.Thank you!