feat(stdlib): add itertools module bindings

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Closes N/A — proactive bindings expansion (Task 8: Bindings Coverage Improvements).

What

Adds F# bindings for Python's [itertools]((docs.python.org/redacted) module — a popular stdlib module with no existing coverage.

Infinite iterators: count, cycle, repeat

Finite iterators: accumulate, chain (2/3/4-arg + chainFromIterable), compress, dropwhile, filterfalse, groupby, islice (stop / start+stop / start+stop+step), pairwise (Python 3.10+), takewhile, zip_longest

Combinatoric iterators: permutations, combinations, combinationsWithReplacement, product

Why

itertools is one of the most commonly used Python stdlib modules, especially for functional-style code — exactly the kind of code F# developers write. It was entirely missing from Fable.Python.

Design notes

• All functions follow the same [<ImportAll("itertools")>] / [<Erase>] pattern used throughout src/stdlib/.
• Functions that Python calls with two positional arguments (accumulate with a binary function) use [<Emit("... lambda a, b: $2(a)(b) ...")] to correctly bridge Fable's curried F# functions to Python's 2-arg callables.
• chain.from_iterable is exposed as chainFromIterable via [<Emit>] since dotted method names can't be expressed in F# identifiers.
• pairwise requires Python 3.10+; this is documented in the XML doc comment.
• groupby returns seq<'K * seq<'T>>; the doc comment warns that group iterators share the underlying iterator (standard Python groupby caveat).
• All return types are seq<'T> (lazy), consistent with Python's iterator semantics. Callers can pipe to Seq.toList etc.

Tests

20 tests added in test/TestItertools.fs covering all major functions.

Note

🔒 Integrity filter blocked 10 items

The following items were blocked because they don't meet the GitHub integrity level.

• How does it generate the python source from AST? #5 list_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• Roadmap #15 list_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• Create Pyi parser #22 list_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• string format specifier '{i:X4}' not working #36 list_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• Support for Attributes? #48 list_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• Pandas binding #65 list_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
• typeshed: generate bindings automatically ~ python glutinum? #115 list_issues: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
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