This fix ensures that the site setting `post_edit_time_limit` does not
bypass the limit of the site setting `min_trust_to_edit_post`. This
prevents a bug where users that did not meet the minimum trust level to
edit could edit the title of topics.
* FEATURE: Add tl2 threshold for editing new posts
* Adds a new setting and for tl2 editing posts (30 days same as old value)
* Sets the tl0/tl1 editing period as 1 day
* FIX: Spec uses wrong setting
* Fix site setting on guardian spec
* FIX: post editing period specs
* Avoid shared examples
* Use update_columns to avoid callbacks on user during tests
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
