Fix built-ins serializer to work with any packages

Make it serialize data for all packages found in sources and not only
KotlinBuiltIns.FQ_NAME, i.e. "jet". This is required to migrate built-ins from
package "jet" to "kotlin"
2 Intentions for string templates:
the first removes curly braces from a simple name variable, ${x} -> $x
and the second does the opposite $x -> ${x}