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Validation: `range` is only allowed as the callee of a for-loop header (#492)

The resolver predeclares the name `range`, so `x = range(3)`, `f = range` or
`print(range(3))` passed validation and then failed (or, on PVML, quietly
worked and produced an iterator value no other engine has) at run time, in a
different way per engine: a NameError on CSE, a leaky "ReferenceError: $range
is not defined" on py2js, a TypeError or silent success on PVML.

Add a validator that rejects every use of `range` except as the callee of a
`for` header, with a clear SyntaxError. Chapters 3 and 4 get
RangeOutsideForHeaderError ("'range' can only be used in a for-loop header");
chapters 1 and 2 have no for loops, so there `range` is just an unknown name
and gets the usual NameNotFoundError. It runs in the shared resolver, so all
engines agree at compile time.

A program that redeclares `range` and then uses it now reports a second error
for the use; the reserved-name error still comes first, and the tests check
that rather than a count of one.

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>

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