Adds support for writing Ion 1.1 null, bool, int, and float binary encoding

[popematt]

Issue #, if available:

None

Description of changes:

• Adds support for WriteBuffer to write FlexInts and FlexUInts from BigIntegers
• Adds OpCodes, a class that holds op code constants
• Adds IonEncoding_1_1, a class that may later be subsumed by a Raw Binary Writer for Ion 1.1. This class contains methods that can write raw Ion values to a WriteBuffer.

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: 204 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
src/com/amazon/ion/BufferConfiguration.java	95.00% <ø> (-5.00%)	⬇️
src/com/amazon/ion/IonBufferConfiguration.java	93.54% <100.00%> (-0.21%)	⬇️
src/com/amazon/ion/IonCursor.java	100.00% <100.00%> (ø)
src/com/amazon/ion/OversizedValueException.java	100.00% <100.00%> (ø)
src/com/amazon/ion/Timestamp.java	89.14% <100.00%> (+0.07%)	⬆️
src/com/amazon/ion/impl/IonReaderTextSystemX.java	61.33% <ø> (+1.24%)	⬆️
src/com/amazon/ion/impl/IonReaderTreeUserX.java	92.04% <100.00%> (+5.83%)	⬆️
...c/com/amazon/ion/impl/LocalSymbolTableImports.java	90.62% <ø> (+2.38%)	⬆️
src/com/amazon/ion/impl/_Private_IonConstants.java	25.64% <ø> (ø)
src/com/amazon/ion/impl/bin/WriteBuffer.java	95.69% <100.00%> (+0.16%)	⬆️
... and 14 more

... and 27 files with indirect coverage changes

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