Improve conformance test runner

[popematt]

Issue #, if available:

None

Description of changes:

• Updates the conformance test runner to support both bytes and binary for binary fragments. This is a temporary change until Resolve 'bytes'/'binary' discrepancy ion-tests#129 is merged and ion-java is updated to have the latest commit of ion-tests.
• Refactors ConformanceTestRunner into an abstract class. We can create one subclass for each reader configuration. This makes it easier to run a subset of tests (which is faster than running all of them) or to focus on a specific reader implementation. We can also have separate skip lists for the different readers if we so choose. It also means that the test report uses the reader configuration as the top level grouping rather than the very lowest level differentiator.
• Updated the test names so that the source file is at the start of every name. E.g. [system_macros/default.ion] the first argument can be a single value

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@                Coverage Diff                 @@
##             ion-11-encoding     #997   +/-   ##
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  Coverage                   ?   70.57%           
  Complexity                 ?     7085           
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  Files                      ?      201           
  Lines                      ?    28215           
  Branches                   ?     5034           
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  Hits                       ?    19912           
  Misses                     ?     6716           
  Partials                   ?     1587           

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