Merge branch 'master' into cte-nesting-support

Merge branch 'master' into cte-nesting-support

* master:
  accommodate for cloned bindparams w/ maintain_key
  Support generics in code to allow Column[int] etc
  accommodate plain core textual statements
  Modernize tests - dml_whereclause
  New issue templates forms
  Add mypy tests on github.
  Fix type
  Version 1.4.23 placeholder
  - 1.4.22
  Apply new uniquing rules for future ORM selects
  Modernize tests - legacy_select
  dont warn for dictionary passed positionally
  implement cache key for return_defaults token
  Documentation improvements
  Encourage primary_key for secondary tables
  guard against unexpected weakref cleanups