Django Evolution's evolution optimization code had issues when applying

a series of evolutions that add a ForeignKey field to a newly-introduced

model that is then renamed in the same batch. The resulting field would

still point to the original model, resulting in a KeyError.
This was partly caused by the optimization code not attempting to update

the related_model attribute of the new field when merging field

attributes, and partly due to the RenameModel mutation not being

available during the evolution process for a newly-introduced model (due

to it being filtered out earlier on).
This change fixes this by adding code for tracking model renames and

deletions, ensuring the RenameModel is always present in the

optimization steps, and making sure that related_model attribute is set

for newly-introduced fields when the specified model has been renamed.
Optimizations were also added to condense model renames, and to remove

any mutations that rename models that will later be deleted.

Unit tests pass for SQLite, MySQL, and PostgreSQL.
Tested against a database that hit this particular bug. I received a

KeyError before the fix, but after, I was able to successfully upgrade.