Improve "rules" for converting usages of external dependencies

[zxbodya]

1. Add support for replacing global types like Intl$DateTimeFormatOptions with expressions like Intl.DateTimeFormatOptions, generate such replacements for built-in types
2. ~~Fix .importFlow - currently it might work not correctly when import needs to be renamed, or can result in duplicated import(which would be babel syntax error)~~
3. Make it possible to use external "rules"
   • finalize the format for rules - what helpers to provide
   • create/expose utilities for generating "rules" and tests for them based on definition files and on usages in the codebase
   • add cli argument allowing to specify external modules with rules to be used