c/validation: clean up GTest matchers, utilities

[lidavidm]

• Add test helper to execute a statement and get back Result<int64_t> (for DDL)
• Reorganize and document the quirks
• Add test helper to execute a statement and get back a single batch (tests assume they will always be a single batch but that isn't necessarily true)
• Create or use utilities for iterating over streams (https://github.com/apache/arrow-nanoarrow/issues/403)
  • Create utilities for asserting on values, preferably using native C++ types for clarity, and so that we can use the native GTest matchers
  • Remove the StreamReader class
  • Consolidate the Handle class
• Create utilities for asserting on schemas more effectively (particularly for parameterized/nested types). Possibly something like the standard GTest ElementsAre.

[lidavidm]

Deferring this to see what the upstream utilities look like