SWEEP: PrintStackTrace cleanup, #932

[paulirwin]

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Clean up usages of Exception.StackTrace and consolidate to new PrintStackTrace/PrintCurrentStackTrace methods.

Fixes #932

Description

There were various inconsistent, and sometimes incorrect, translations of .printStackTrace() to .NET. This moves the PrintStackTrace extension method into Support, makes it print any Suppressed exceptions, and updates all usages where Lucene uses printStackTrace on a caught exception to use this new extension method.

In the case where the Lucene code was doing new Throwable().printStackTrace(...) to print the stack trace at the call site, this has been replaced with the new StackTraceHelper.PrintCurrentStackTrace(TextWriter) method. This method skips the frame of itself in the stack trace, and has NoInlining set to prevent inlining which could cause the top stack frame to be missed.

For suppressed exceptions, it will print them below the string output of the exception if there are any. This PR does not change the structure of suppressed exceptions, i.e. to use AggregateException as discussed in #932, as there didn't seem to be a good seam for doing that at this time.

[paulirwin]

FYI, tests failing on .NET FX, I'll get that fixed later today.