Improve the diagnostic message emitted on failure to parse metadata.json

[jcbollinger]

Use Case

If a syntax error is introduced into a module's metadata.json file then subsequent use of PDK on that module fails with a misleading and unhelpful error message:

pdk (ERROR): This module is not PDK compatible. Run pdk convert to make it compatible with your version of PDK.

Describe the Solution You Would Like

In the event that PDK fails to parse metadata.json, it should diagnose that issue specifically, with as much context as possible. For example, something more like "Syntax error in metadata.json, line 8, column 17".

Describe Alternatives You've Considered

The main alternative is to leave the diagnostic messaging as it now is. Although it could be argued that the current messaging is technically correct, it does not help users identify or fix the problem.

Additional Context

PDK does not currently offer tools for maintaining metadata.json, so it is normal for that file to be edited by hand from time to time even in PDK-compatible modules. It is natural that editing such files by hand occasionally introduces syntax errors, so it is to be expected that this issue will manifest relatively frequently for a wide variety of module maintainers. I know it happened to me several times before I was sufficiently motivated to write this feature request.