Remove deprecated method ActiveRecord::Migrator.proper_table_name
Merge pull request #15512 from akshay-vishnoi/delete-deprecated-method

Remove deprecated method ActiveRecord::Migrator.proper_table_name
Fix behavior of handling BC era dates.

BC era year is (astronomical year + 1) and starts from 1 BC.
Avoid hardcoded value in test setup/teardown.
Merge pull request #15525 from zuhao/refactor_actionpack_query_string_parsing_test

Avoid hardcoded value in test setup/teardown.
Mime::PNG is already defined.
Merge pull request #15521 from edogawaconan/fix_bc_postgres_master

Fix BC year handling in postgres
Merge pull request #15529 from zuhao/refactor_actionpack_mime_type_test

Make sure Mime::Type is not altered after tests.
Avoid hard-coded value in test setup/teardown.
Restore Response.default_headers after test.
Merge pull request #15531 from zuhao/refactor_actionpack_request_test

Avoid hard-coded value in test setup/teardown.
Merge pull request #15532 from zuhao/refactor_actionpack_response_test

Restore Response.default_headers after test.