Support GoogleSQL inline aggregate WHERE filter: AGG(expr WHERE cond)

[moshap-firebolt]

GoogleSQL/BigQuery allow an inline WHERE filter inside an aggregate call, e.g.
COUNT(* WHERE cond), SUM(x WHERE cond), ARRAY_AGG(x WHERE cond ORDER BY y).
It is the in-argument spelling of the standard AGG(x) FILTER (WHERE cond).

Changes

• Add FunctionArgumentClause::Where(Expr).
• Parse it in parse_function_argument_list for the BigQuery and Generic
  dialects (before ORDER BY / LIMIT / HAVING).
• Render it in Display (WHERE <expr>) and compute its span.
• New test parse_aggregate_with_where_filter in tests/sqlparser_bigquery.rs.

Used by Firebolt's dialect=bigquery path to lower AGG(x WHERE c) to
AGG(x) FILTER (WHERE c). Intended for eventual upstreaming to apache/datafusion-sqlparser-rs.

🤖 Generated with Claude Code

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Note

Low Risk
Scoped parser/AST extension for two dialects with tests; no changes to auth, data paths, or existing clause behavior beyond the new optional WHERE branch.

Overview
Adds support for GoogleSQL/BigQuery inline aggregate filters such as COUNT(* WHERE x > 1) and SUM(x WHERE y > 0)—the in-argument form of standard FILTER (WHERE …).

A new FunctionArgumentClause::Where(Expr) AST variant is introduced and parsed in parse_function_argument_list for Generic and BigQuery dialects immediately after the comma-separated arguments and before ORDER BY / LIMIT / HAVING. Display renders WHERE <expr> and Spanned uses the filter expression’s span.

BigQuery tests cover round-trip parsing for simple aggregates and ARRAY_AGG(… WHERE … ORDER BY …), and assert the clause is stored as FunctionArgumentClause::Where.

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[moshap-firebolt]

Reverted this from main — it was targeted at the wrong branch. main mirrors apache upstream (which carries the breaking ORDER BY AST change apache#2246 that packdb's dialect translator can't read), so packdb can't pin main. The change has been cherry-picked onto the stable pin line instead: branch firebolt/v0.62.0-patches (v0.62.0 + our cherry-picks, no apache#2246), commit eee77cb, which packdb now pins. Upstream PR: apache#2404.