Add new functions to Series and Expressions, some docs update

[fbx31]

New functions in src\lazy\dsl.rs

• add implode, str_strip_chars, str_starts_with, str_ends_with
• add expression support in str_replace and str_replace_all
• add struct_field_by_index, struct_with_fields

Update documentation for Series in polars/series/*

• replaced ListNamespace by SeriesListFunctions (ListSeries in doc) and StringNamespace by SeriesStringFunctions (StringSeries in doc)
• renamed SeriesDateFunctions by DatetimeSeries and SeriesStructFunctions by StructSeries

Unfortunately Namespaces are not consistent between Series and Lazy with current polars sources (or I didn't succeed to align them).
So not sure that Namespaces in shared_traits are very usefull.

Update implementation and documentation for Expr in polars/lazy/expr/*

• convert ExprDateTime from type to interface and ExprList from type to interface
• add nth and withFields in interface ExprStruct
• for strings: change signatures of contains, extract, replace and replaceAll to support Expressions, new functions endsWith, startsWith, stripChars, stripCharsEnd, stripCharsStart

Add new tests

• in tests/series.test.ts for "str contains" and "struct:nth"
• in tests/expr.test.ts for "expr:implode", "str:endsWith", "str:starsWith", "str:replace", "str:replaceAll", "struct:nth", "struct:withFields", "str:stripChars"

2 new added tests are still skipped with comment "// TODO: Remove skip when polars-plan will support for "dynamic pattern length in 'str.replace' expressions""

Lint on rust (cargo fmt) and typescript (biome) OK

Doc generation OK : typedoc --> [warning] Found 0 errors and 358 warnings

Tests passed
Test Suites: 14 passed, 14 total
Tests: 3 skipped, 3 todo, 1052 passed, 1058 total
Snapshots: 0 total
Time: 26.468 s, estimated 30 s
Ran all test suites.

Configuation used

• Windows (sorry in advance for the CR/LF burden)
• nodejs v22.11.0
• npm v10.9.0 (no use or yarn)
• biome v1.9.4
• typedoc v0.27.9
• typescript v5.7.2
• cargo/rustc v1.85.0-nightly

[universalmind303]

Sorry for the delayed review. Looks good @fbx31. Thanks!