firebase-ios-sdk

Add LLDB type summaries for Firestore types (#5407)

There are some particular pain points debugging Firestore today because contents of variables are obscured due to information hiding and shared representation techniques we use. Also, we use elements of the Abseil library to supplement what's available in the C++11 standard library.

Taken together, these make our default experience in LLDB and the Xcode debugger quite painful: getting the path of a document currently takes 5 clicks. This change pulls the document path into the summary line, making it available with no clicks.

This change adds type summaries for

  * DocumentKey and ResourcePath
  * DocumentReference and FIRDocumentReference
  * DocumentSnapshot and FIRDocumentSnapshot
  * absl::optional
  * DatabaseId