Order of rewrites in logprob submodule is not respected

[ricardoV94]

Description

I could be wrong, but when working on #6072, it seemed that the order of the rewrites in the database is only respected when using the kwarg position. Otherwise it seems to be ignored, and only the order of definition matters.

So:

pymc/pymc/logprob/rewriting.py

Line 263 in e0d25c8

logprob_rewrites_db.register("measurable_ir_rewrites", measurable_ir_rewrites_db, -10, "basic")

Should be:

logprob_rewrites_db.register( 
     "measurable_ir_rewrites", measurable_ir_rewrites_db, "basic", position=-10, 
 )

We should probably also leave an offset between pre-canonicalize and measurable_ir_rewrites (both are supposed to be at -10) in case anyone wants to introduce rewrites between those two phases.