Adds read support for Ion 1.1 system symbols

[popematt]

Issue #, if available:

None.

Description of changes:

• Adds support for reading system symbols in FlexSyms and using the EE op code.
• Changes a lot of tests from using A0 for "unknown symbol" to 60 and 90 for empty symbol to 75.
• Removes the @Disabled annotation from disabled tests in IonManagedWriter_1_1_Test
• Adds the byte value to the string representation of IonTypeID. (I.e. was SYMBOL(1), now 0xEE(SYMBOL,1)) That was useful to me while debugging things.
• Limitations:
  • I disabled the entirety of EncodingDirectiveCompilationTest. For some reason, I couldn't seem to understand how these tests were supposed to work in the first place, so I was unable to update them to get them to work with my changes. Because almost all of the other tests are working, I am fairly confident that the problem lies in the tests rather than in the changes I've made. I will need to figure this out and update, replace, or remove this test class, but I didn't want to block this PR on it.
  • There's a bit of a hacky way of handling system symbols that are encoded as tagless flexsyms. There's a rather long FIXME: note about it in the code. This works for now... but should probably be fixed.
  • It can't match read encoding directives/symbol tables that use user-space equivalents of the system symbols. This is something that MUST be fixed eventually.
  • I disabled the Ion 1.1 round-trip tests that transfer values using the system reader because it doesn't translate the symbol tables correctly at this point and/or it can't read them because of the aforementioned issue.

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.18797% with 33 lines in your changes missing coverage. Please review.

Please upload report for BASE (ion-11-encoding@4b373e5). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...on/impl/IonReaderContinuableApplicationBinary.java	67.39%	9 Missing and 6 partials :warning:
...mazon/ion/impl/IonReaderContinuableCoreBinary.java	75.00%	4 Missing and 5 partials :warning:
...main/java/com/amazon/ion/impl/IonCursorBinary.java	81.81%	1 Missing and 5 partials :warning:
src/main/java/com/amazon/ion/impl/IonTypeID.java	80.00%	1 Missing :warning:
...a/com/amazon/ion/impl/LocalSymbolTableImports.java	80.00%	0 Missing and 1 partial :warning:
...va/com/amazon/ion/impl/bin/IonManagedWriter_1_1.kt	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## ion-11-encoding #944 +/- ## ================================================== Coverage ? 70.05% Complexity ? 6870 ================================================== Files ? 196 Lines ? 27070 Branches ? 4899 ================================================== Hits ? 18964 Misses ? 6593 Partials ? 1513 ```

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