Add JsonProtocol.serializeRecover

[jackkoenig]

This function will safely wrap any unserializeable annotations in
UnserializeableAnnotations so that they can be safely serialized to JSON
for logging.

Follow on to #1885, makes -ll trace much more useful if you happen to have 1 unserializable annotation making your whole log worthless.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• [NA] Did you update the FIRRTL spec to include every new feature/behavior?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you state the API impact?
• Did you specify the code generation impact?
• Did you request a desired merge strategy?
• Did you add text to be included in the Release Notes for this change?

Type of Improvement

• new feature/API

API Impact

There is a new public method, JsonProtocol.serializeRecover which will always succeed because it wraps any unserializable annotations in UnserializableAnnotations with the error and .toString of the underlying Annotation as contents.

Backend Code Generation Impact

None

Desired Merge Strategy

• Squash

Release Notes

• Add new JsonProtocol.serializeRecover which wraps unserializable annotations in UnserializableAnnotations so that a valid JSON is always created.
• Use this new API in --log-level trace so that the logged annotations are always useful, even when there are unserializable annotations

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels?
• Did you mark the proper milestone (1.2.x, 1.3.0, 1.4.0) ?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you mark as Please Merge?