feat: Initial SQL support for INTERVAL strings

[alexander-beedie]

Closes #16702.

Adds initial INTERVAL '...' support to the SQL interface, covering typical uses (follow-ups listed below).

Handles all the typical units in verbose and abbreviated form, is case-insensitive and whitespace tolerant, and also ignores commas (all of which are valid for PostgreSQL interval literals).

• Extends our existing Duration object with a new parse_interval option.
• Also adds "Literal" and "Neg" trait implementations to Duration.

Example

import polars as pl

with pl.SQLContext(df=None, eager=True) as ctx:
    df = ctx.execute(
        """
        SELECT
          INTERVAL '1w2h3m4s' AS i1,
          INTERVAL '100ms, 100us' AS i2,
          INTERVAL '1 quarter 2 months 987 microseconds' AS i3,
        FROM df
        """
    )
    # shape: (1, 3)
    # ┌──────────────┬──────────────┬──────────────┐
    # │ i1           ┆ i2           ┆ i3           │
    # │ ---          ┆ ---          ┆ ---          │
    # │ duration[ns] ┆ duration[ns] ┆ duration[ns] │
    # ╞══════════════╪══════════════╪══════════════╡
    # │ 7d 2h 3m 4s  ┆ 100100µs     ┆ 140d 987µs   │
    # └──────────────┴──────────────┴──────────────┘

Follow-ups

• Parsing support for negative interval components, eg: '7d -1 h 30m -10s'.
• Parsing support for the alternative "cast" form '1y6m'::interval.
• Parsing support for non-constant intervals, eg: INTERVAL col || ' years'.
• Better Duration behaviour (generally, not SQL-specific) with ops and incorrect supertype conversion (eg: Multiplying or dividing pl.duration converts to float #16514)

[codecov]

Codecov Report

Attention: Patch coverage is 65.78947% with 39 lines in your changes missing coverage. Please review.

Project coverage is 81.43%. Comparing base (ddf8126) to head (54f9105).

Files	Patch %	Lines
crates/polars-time/src/windows/duration.rs	64.55%	28 Missing ⚠️
crates/polars-sql/src/sql_expr.rs	60.71%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16732      +/-   ##
==========================================
- Coverage   81.45%   81.43%   -0.03%     
==========================================
  Files        1413     1413              
  Lines      186096   186182      +86     
  Branches     2776     2776              
==========================================
+ Hits       151588   151608      +20     
- Misses      33988    34054      +66     
  Partials      520      520              

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