Add rewrite for `log(gamma) -> gammaln`

Description

We're missing this simple rewrite:

import pytensor.tensor as pt
from pytensor.graph import rewrite_graph

x = pt.scalar("x")
out = pt.log(pt.gamma(x))
new_out = rewrite_graph(out, include=("canonicalize", "stabilize", "specialize"))
new_out.dprint()

Can be done easily with PatternNodeRewriter as in

https://github.com/pymc-devs/pytensor/blob/911c6a33c2bea6bf1d5b628154e84c43cbed1c63/pytensor/tensor/rewriting/math.py#L3646-L3651

We could also add rewrites for common combinatorics expressions like

naive_betaln = pt.log((pt.gamma(x) * pt.gamma(y)) / pt.gamma(x + y)
betaln = pt.gammaln(x) + pt.gammaln(y) - pt.gammaln(x + y)

https://github.com/pymc-devs/pytensor/blob/ad55b69f3d13f11c6a9a57823c2a88a966db8b1a/pytensor/tensor/special.py#L799-L804

Or for log(poch): https://github.com/pymc-devs/pytensor/blob/ad55b69f3d13f11c6a9a57823c2a88a966db8b1a/pytensor/tensor/special.py#L767-L772

For these more general cases we can probably use something more flexible than the PatternNodeRewriter. We want to apply as long as we know all the terms inside are factorials/gammas/exps (positive things that easily blow up). This is a narrow/easier subset of https://github.com/pymc-devs/pytensor/discussions/177

Start in pytensor/tensor/rewriting/math.py at the PatternNodeRewriter example around lines 3646-3651, then inspect the related gammaln, betaln, and poch definitions in pytensor/tensor/special.py. Run the issue's rewrite_graph example and implement the log(gamma) to gammaln rewrite; done means the rewritten graph uses gammaln for this expression.