… (STID 1941-1bfa)

A query like `f(1, 2 IN ((3 IN (4, 5)) AS x))` triggered a
`Logical error: 'Inconsistent AST formatting between 'ExpressionList' and
'ExpressionList'` (STID 1941-1bfa) abort in debug / sanitiser builds
because the format-parse-format round-trip in `DB::executeQueryImpl`
diverged by the inner `(3 IN (4, 5))` parens.

`ASTFunction::formatImplWithoutAlias` wraps an `IN` expression in `(...)`
via `need_parens_around_in` whenever the IN sits inside a multi-argument
function call (`frame.current_function != nullptr`), so the first format
emits `f(1, (2 IN ((3 IN (4, 5)) AS x)))`. The re-parse sets
`parenthesized=true` on the outer `IN`, and on the second format
`IAST::format` emits the outer parens via the `parenthesized` path in
`decideParensEmission`, which clears `frame.current_function`. The inner
`IN` then sees `in_function_args == false` and stops emitting its own
`(...)`, so the inner `(3 IN (4, 5))` parens disappear and the second
format differs from the first.

Fix: when the outer `IN`'s `formatImplWithoutAlias` emits the wrapping
`(...)` via `need_parens_around_in`, also clear `current_function` for
descendants. Both wrapping paths (this one and the `parenthesized` path
in `IAST::format`) now produce the same output, so the round-trip is
stable.

CI: https://s3.amazonaws.com/clickhouse-test-reports/json.html?PR=103126&sha=9ebf9fa83a0839baba782baf9689bc849215dc5a&name_0=PR&name_1=AST%20fuzzer%20%28amd_debug%2C%20targeted%2C%20old_compatibility%29
PR: ClickHouse#103126

…sted-1941-1bfa

Per ClickHouse#105091 (comment),
replace each `SELECT formatQuerySingleLine(q)` with the explicit invariant
the test is trying to express:

    formatQuerySingleLine(formatQuerySingleLine(q)) = formatQuerySingleLine(q)

which is exactly `format_2 == format_1` — the assertion `DB::executeQueryImpl`
runs in debug / sanitiser builds. The previous form pinned the first-pass
output text and would still pass if a future regression kept the first pass
unchanged but broke the second pass; the equality form proves the
round-trip-stability invariant directly. Reference becomes a column of `1`s.