fix: add ParseTime transpilation for BigQuery to DuckDB

[william-goode]

Summary

BigQuery's PARSE_TIME is parsed into exp.ParseTime but DuckDB's generator has no handler for it. The expression falls through to function_fallback_sql, which emits PARSE_TIME(...) verbatim — DuckDB rejects this since it has no such function.

Fix: Add a parsetime_sql method to DuckDBGenerator that mirrors the existing strtodate_sql pattern: STRPTIME + CAST to TIME, with TRY_STRPTIME for SAFE expressions.

Reproduction

import sqlglot

# Works
sqlglot.transpile("SELECT PARSE_DATE('%Y-%m-%d', '2023-01-15')", read="bigquery", write="duckdb")
# => ["SELECT CAST(STRPTIME('2023-01-15', '%Y-%m-%d') AS DATE)"]

# Broken (before this fix)
sqlglot.transpile("SELECT PARSE_TIME('%H:%M', '14:30')", read="bigquery", write="duckdb")
# => ["SELECT PARSE_TIME('14:30', '%H:%M')"]  -- DuckDB rejects this

# After this fix
# => ["SELECT CAST(STRPTIME('14:30', '%H:%M') AS TIME)"]

Test plan

• Added validate_all test for BigQuery PARSE_TIME → DuckDB CAST(STRPTIME(...) AS TIME)
• Full test suite: 1111 passed, 18119 subtests passed
• BigQuery and DuckDB dialect tests both green

[geooo109]

@william-goode great work! thanks for the pr