…n they shouldn't be.

…harmap.

…ngs in EncodingManager.

A side effect of this change is we're no longer updating the JRuby runtime's default_external and default_internal values. As a result, we can't use methods from the JRuby runtime that rely on those values being up-to-date. Since RubyString#inspect is one such method, we have to move that back out to Ruby (String#inspect). This code has ping-ponged a few times between a Ruby and Java implementation. It appears whatever issue forced the move back to Java (i.e., RubyString#inspect) has been addressed.

…codings.

Also, started moving non-standard Encoding methods out to Truffle::Encoding.

These methods became a lot simpler once we started tracking default_external and default_internal encodings in the EncodingManager.