Adds implementations of repeat, make_field, and make_blob

[popematt]

Issue #, if available:

None

Description of changes:

• Adds implementations of make_field, make_blob and repeat.
• Both make_field and repeat need to be able to track some state over their evaluation, so I added a field to ExpansionInfo that Expanders can use for that purpose rather than having to create a pool of various Expander instances.
• There are a few drive-by fixes
  • in MacroEvaluator, updated MakeStringExpander and MakeSymbolExpander to not accept null, as per the spec.
  • in MacroEvaluatorTest, updated comments to have the (%x) syntax for argument expansion.

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

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 14 lines in your changes missing coverage. Please review.

Please upload report for BASE (ion-11-encoding@257ecfe). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...n/java/com/amazon/ion/impl/macro/MacroEvaluator.kt	77.77%	9 Missing and 5 partials ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##             ion-11-encoding     #972   +/-   ##
==================================================
  Coverage                   ?   70.36%           
  Complexity                 ?     7028           
==================================================
  Files                      ?      200           
  Lines                      ?    27634           
  Branches                   ?     4993           
==================================================
  Hits                       ?    19444           
  Misses                     ?     6626           
  Partials                   ?     1564           

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