revert primary_key=True change and replace with inline_primary_key

revert primary_key=True change and replace with inline_primary_key

Reverted the behavior of :meth:`.Operations.add_column` that would
automatically render the "PRIMARY KEY" keyword inline when a
:class:`.Column` with ``primary_key=True`` is added. The automatic
behavior, added in version 1.18.2, is now opt-in via the new
:paramref:`.Operations.add_column.inline_primary_key` parameter. This
change restores the ability to render a PostgreSQL SERIAL column, which is
required to be ``primary_key=True``, while not impacting the ability to
render a separate primary key constraint. This also provides consistency
with the :paramref:`.Operations.add_column.inline_references` parameter and
gives users explicit control over SQL generation.

Fixes: #1232
Change-Id: Ia9333c1768caa5d99b0527d59fcc797af2c3249c