User.get_profile() and User.get_site_profile() have diverged over

time, in terms of implementation and usage. get_profile() used to only

fetch profiles, requiring them to be created through some other means,

but these days it's guaranteed to return a result. It also gained the

ability to fetch via cache. get_site_profile() still worked like the

old get_profile() did, however, and required a lot more work from

callers. Much of the code in the codebase using these methods were

outdated and doing too much, creating extra SQL queries and ignoring any

previously-cached profiles.
This change works to modernize profile lookups and usage. Both methods

now accept the same arguments.


cached_only controls whether to only consider profile results in the

  existing cache.


create_if_missing controls whether to create an entry in the

  database if it doesn't already exist (which now defaults to True for

  both, creating consistent behavior).


return_is_new alters the return value to return a tuple containing

  the profile and an is_new boolean, letting callers be a bit smarter

  about whether operations on a profile need to be performed.


Call sites have been updated to take advantage of the new arguments and

behavior. Many callers that previously did their own get_or_create()

now benefit from the cache. Old calls checking for exceptions no longer

need to, or now pass create_if_missing=False. Default values computed

in the absence of a profile have been removed.
We also had many places where we were saving the entirety of profiles

unnecessarily. In some cases, we'd be performing a double-save of the

same data. We now no longer do this, and when we do want to save, we're

explicit about what fields we're updating. This helps avoid conflicts

and reduces database writes.

All unit tests pass.
Went through the product and tested most affected areas. There is a

chance of some subtle fallout/behavioral changes, which will require

further testing on reviews.reviewboard.org.