metafiles: reduce pathname conversions in #include?
metafiles: extract constant arrays
metafiles: remove unused method
metafiles: combine #should_copy? and #include?
Eliminate FORMULA_META_FILES constant
Simplify Pathname#install_metafiles
PyPy 2.3.1

Closes #29966.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
metafiles: simplify #copy? further