[moshap-firebolt]

Replaces the fork's own fix for (x) -> lambda chains from #18 with the upstream version, apache/datafusion-sqlparser-rs#2699. The cherry-pick of upstream apache#2619 (nested POSITION calls), also in #18, stays.

Reverts the lambda half of #18, then cherry-picks apache#2699's two commits unchanged. The src/, test and fuzz-seed changes are identical, line for line, to apache#2699; only conflict context (a neighbouring cache field, test-file tail) differs. The fork's full suite (--all-features), fmt and clippy are clean.

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Note

Medium Risk
Touches expression-prefix dispatch and failure memoization for lambda vs binary ->, which can change parse trees on edge-case SQL; risk is mitigated by targeted regression tests and upstream parity.

Overview
Ports upstream apache#2699 for arrow lambda parsing and memoization, replacing the fork’s earlier lambda-chain fix while keeping the nested POSITION work from the same effort.

In try_parse_lambda, comments and the failure-cache key are clarified (memo_key); behavior is still to memoize failed (<params>) -> <body> attempts so long (x) -> … chains cannot trigger exponential retries when the body does not parse.

Tests are rewritten: the blowup guard uses a shorter chain and asserts every lambda-capable dialect rejects the bad SQL quickly; dispatch coverage now checks concrete AST shapes (nested lambdas, -> fallback when (1) is not a param list, cached vs uncached failure). A fuzz seed for Databricks-style lambda chains is added and excluded from RAT checks.

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