Add repeatability tests for when the range of the integers is `2**32`
(and `2**32 +/- 1` for good measure) with broadcasting.  The underlying
functions called by Generator.integers and random.randint when the
inputs are broadcast are different than when the inputs are scalars.

Assert that an invalid value (2**n-1 for n = 8, 16, 32, 64) has not
been passed to the Lemire function.

When the input to Generator.integers was 2**32, the value 2**32-1
was being passed as the `rng` argument to the 32-bit Lemire method,
but that method requires `rng` be strictly less then 2**32-1.

The fix was to handle 2**32-1 by calling next_uint32 directly.
This also works for the legacy code without changing the stream
of random integers from `randint`.

Closes gh-16066.

BUG: Alpha parameter must be 1D in `generator.dirichlet`

Only one dimensional alpha paramter is currently supported, but higher
dimensions were silently allowed and gave an incorrect results. This
fixes the regression. In the future, the API could be extended to allow
higher dimensional arrays for alpha.

Fixes gh-15915