This PR provides a draft implementation for the proposal described at#849.

Thetransformer.transformGoFile method contains some code that computes the obfuscated identifier for a giventypes.Object.

This patch does essentially two things:

1. it refactors thetransformer.transformGoFile method, lifting the code segment mentioned above into an independently callable method namedtransformer.obfuscateObjectName;
2. it adds a new subcommandgarble map that uses the newly added methodtransformer.obfuscateObjectName to compute the output described atsupport Wails with its use of reflection on types #849.

The refactoring step is necessary to ensure thegarble map command stays in sync with the algorithm used bytransformGoFile.

I have not added a test yet because I am not familiar with the scripting language and it is also not entirely clear to me what the best approach would be for testing the new command.

The implementation of the new command resembles vaguely that of thereverse subcommand:

• it lists all packages provided on the command line, including transitive dependencies;
• for each listed andobfuscated package:
  • it configures a transformer instance, parses and typechecks package files, loads the package cache entry and computes field-to-struct mappings;
  • it visits the full syntax tree looking for identifiers, skipping statements because local identifiers are not relevant here;
  • for each identifier it encounters:
    • it uses type info to resolve the identifier to itstypes.Object;
    • it discards invalid identifiers, objects from other packages and duplicates;
    • it callstransformer.obfuscatedObjectName on the current object;
    • it usesgolang.org/x/tools/go/types/objectpath to compute a path for the current object;
    • if the current object is obfuscated and has a path, it is recorded onto the result map.
• finally, it converts the result map to JSON.