Port trivial production fixes from Lucene 4.8.1, #1381 Batch 1

[paulirwin]

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Backport trivial production fixes from Lucene 4.8.1

Partial #1381 (Batch 1)

Description

• LUCENE-5635 (partial): move stream.Reset() into the try block
• LUCENE-5668: fix off-by-one error in TieredMergePolicy + test
• LUCENE-5656 (partial): don't leak dv producers if one of them throws exception
• LUCENE-5644 (partial): add PulseAll call to DeactivateUnreleasedStates

Note that the partial items will be fully completed in Batch 5.

[Copilot]

Pull request overview

Backports a first batch of small but production-relevant Lucene 4.8.1 fixes into Lucene.Net, focusing on correctness around merging, docvalues resource handling, token stream lifecycle, and thread coordination, plus adding a regression test for the TieredMergePolicy change.

Changes:

• Hardened and corrected several production code paths (token stream reset handling, docvalues producer ref-count/leak behavior, merge “over budget” selection, and thread wakeups).
• Added an argument-range guard to OfflineSorter.ByteSequencesWriter.Write() to prevent invalid short length truncation.
• Added a new TieredMergePolicy regression test for LUCENE-5668.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Lucene.Net/Util/OfflineSorter.cs	Adds len > short.MaxValue guard before writing length as short.
src/Lucene.Net/Index/TieredMergePolicy.cs	Fixes LUCENE-5668 by adjusting the “over budget” eligibility threshold.
src/Lucene.Net/Index/SegmentReader.cs	Prevents docvalues producer reference leaks by tracking gens only after successful producer creation.
src/Lucene.Net/Index/DocumentsWriterPerThreadPool.cs	Ensures waiting threads are woken after deactivating unreleased thread states.
src/Lucene.Net/Index/DocInverterPerField.cs	Moves TokenStream.Reset() into the try so failures are handled and the stream is properly closed.
src/Lucene.Net.Tests/Index/TestTieredMergePolicy.cs	Adds TestUnbalancedMergeSelection() for LUCENE-5668.

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[paulirwin]

The OfflineSorter changes were reverted and moved to #1422.