[SR-3925] Augment the type metadata representation with more semantic information

[ematejska]

Previous ID	SR-3925
Radar	rdar://problem/31411214
Original Reporter	@ematejska
Type	Bug
Status	Resolved
Resolution	Won't Do

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, AffectsABI
Assignee	None
Priority	Medium

md5: 4ec81c861e0f0153c2c74b8dc49a613a

Issue Description:

Ahead of ABI Stability, present more semantic information in the type metadata to enable better future tooling and features such as reflection.

[bob-wilson]

@swift-ci create

[bob-wilson]

Complete reflection support is not a goal prior to ABI stability. We will leave space in the metadata structure so that we can add more semantic information later (SR-3923). Since the task here was to evaluate whether we need to do anything before ABI stability, we can close this now.