Fix migrations with enable_extension

When using ActiveRecord::Base.table_name_prefix and/or
table_name_suffix, extension names got the same treatment as table names
when running migrations. This led to migrations that tried to call, for
example, enable_extension("prefix_hstore") on the connection.
Merge pull request #10798 from jcxplorer/fix-enable_extension-with-table_name_prefix

Fix migrations that use enable_extension with table_name_prefix/suffix

Conflicts:
	activerecord/CHANGELOG.md
	activerecord/lib/active_record/migration.rb
Fixing test order issues