Add a _Private_IonConstants.ARRAY_MAXIMUM_SIZE

[jobarr-amzn]

Description of changes:

Arrays in Java must be indexed by integers (JLS 10.4), but the true maximum array size may be less than Integer.MAX_VALUE. True maximum array size is a JVM implementation detail, and varies by type and by JVM. We have this pinned at Integer.MAX_VALUE - 8 because that's a fairly common value in the JDK itself, in classes such as ConcurrentHashMap, InputStream, Hashtable, ByteArrayChannel, etc.

In testing against a variety of JVMs and types the smallest maximum size I've seen is Integer.MAX_VALUE - 2, and the smallest maximum size I've seen reported is Integer.MAX_VALUE - 6

This change adds a constant _Private_IonConstants.ARRAY_MAXIMUM_SIZE and uses the new constant where appropriate.

Need for this safeguard was exposed by another bug which caused excessive buffering in this chunk of IonCursorBinary:

ion-java/src/main/java/com/amazon/ion/impl/IonCursorBinary.java

Lines 502 to 511 in 3c1b6b1

	int maximumFreeSpace = refillableState.maximumBufferSize;
	int startOffset = (int) offset;
	if (minimumNumberOfBytesRequired > maximumFreeSpace) {
	refillableState.isSkippingCurrentValue = true;
	return false;
	}
	long shortfall = minimumNumberOfBytesRequired - refillableState.capacity;
	if (shortfall > 0) {
	int newSize = (int) Math.min(Math.max(refillableState.capacity * 2, nextPowerOfTwo((int) (refillableState.capacity + shortfall))), maximumFreeSpace);
	byte[] newBuffer = new byte[newSize];

While that is still under investigation, this at least should prevent Requested array size exceeds VM limit.

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

Comparison is base (3c1b6b1) 67.23% compared to head (a4bf716) 67.25%.

Files	Patch %	Lines
src/main/java/com/amazon/ion/apps/BaseApp.java	0.00%	1 Missing ⚠️
...c/main/java/com/amazon/ion/impl/BlockedBuffer.java	0.00%	1 Missing ⚠️
...java/com/amazon/ion/impl/IonReaderTextSystemX.java	0.00%	0 Missing and 1 partial ⚠️
.../main/java/com/amazon/ion/impl/_Private_Utils.java	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #708      +/-   ##
============================================
+ Coverage     67.23%   67.25%   +0.02%     
- Complexity     5484     5488       +4     
============================================
  Files           159      159              
  Lines         23025    23030       +5     
  Branches       4126     4128       +2     
============================================
+ Hits          15481    15489       +8     
+ Misses         6262     6260       -2     
+ Partials       1282     1281       -1     

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[tgregg]

Looks good