Raise clearer errors for constructor, mask, and attribute misuse - #606

A Vector mask on a full-Matrix operation (ewise, extract, .new) leaked a raw
cffi error, "initializer for ctype 'struct GB_Matrix_opaque'", which says
nothing about masks.  The Vector-output direction was already guarded;
_check_mask now guards the Matrix-output direction the same way and reports
"Mask object must be type Matrix; got ...".

The check is gated behind a strict_kind flag rather than applied everywhere,
because assignment is a genuine exception: a Vector mask on a Matrix
row/column assign is valid, and Matrix.__setitem__ validates it separately.
So strict_kind is False for __setitem__ updates and True for .new() and other
full-tensor operations.

Two common misuses failed with a bare "no attribute" message that gave no
direction:

    A.new()           is the expression resolver, not an instance method
    A.transpose()     transpose is the .T property, not a method

A __getattr__ on BaseType supplies the hint on the attribute miss.  It
raises AttributeError, exactly as before, so hasattr() and getattr() with a
default keep answering the way they did and duck-typing probes are
unaffected; only the message changes.  Names with no hint keep the plain
message.

.new and .transpose ride in one commit because they are one mechanism: a
single __getattr__ consulting a single hint table.  Splitting them would mean
adding the same function twice.

__getattr__ fires only on a genuine attribute miss, since slots and methods
resolve first, so the attribute hot path is untouched.

There is deliberately no class-level hint (Matrix.new): that needs a
metaclass, and both candidates break something real.  A plain type
metaclass makes mixing Matrix into any abc-based class die with
"metaclass conflict", and an ABCMeta-derived one leaks register,
__abstractmethods__ and _abc_impl into dir(Matrix), which the
expression-surface guard rightly reports as drift.  Class-level misuse
keeps Python's default AttributeError, and test_abc_mixin_subclass pins
the abc composition.