Add Tracing::Trace for method-based tracing

[rmosolgo]

Implements #4313

When tracing only Hashes:

- Total allocated: 5732040 bytes (28113 objects)
+ Total allocated: 3882696 bytes (17105 objects)

Remaining Hash allocations after this change, just FYI

      4010  /Users/rmosolgo/code/graphql-ruby/lib/graphql/schema/member/has_arguments.rb:114
      4001  /Users/rmosolgo/code/graphql-ruby/lib/graphql/schema/member/has_arguments.rb:265
      4001  /Users/rmosolgo/code/graphql-ruby/lib/graphql/schema/member/has_arguments.rb:286
      3001  /Users/rmosolgo/code/graphql-ruby/lib/graphql/schema/field.rb:808
      1001  /Users/rmosolgo/code/graphql-ruby/lib/graphql/execution/interpreter/runtime.rb:41
      1001  /Users/rmosolgo/code/graphql-ruby/lib/graphql/execution/interpreter/runtime.rb:65

TODO:

• Make each schema class have its own tracer class that inherits from its superclass's tracer class
  • Add behaviors via modules ... dsl? tracer_module(...)?
  • How to keep options separate between modules? punt
• update tests to use this new API
• build a compatibility layer that calls old-style tracing (strings) from a new-style tracing object
• Update the built-in tracers
• Decide if/how to handle backtrace: true punt
• Make sure it works with shopify/graphql-metrics
• Update the docs