Fix SegmentInfos replace doesn't update userData

[tohidemyname]

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Summary of the changes (Less than 80 chars)

Fixes #{bug number} (in this specific format)
#947

Description

{Detail}

[paulirwin]

@tohidemyname Thanks for this PR!

@NightOwl888 This appears to be a pretty straightforward port of apache/lucene#12626 which was in Lucene 9.9.0. Given the single-line nature of the change, I think this is probably safe to backport. Let me know if you agree. I'll tidy it up with a comment explaining the backport so we're aware for future porting efforts.

[NightOwl888]

@paulirwin - Thanks for finding that PR. The fact that a link or mention of it was missing from both the issue and PR was the primary thing holding this up.

I see a few issues that should be addressed before merging it.

• 1. The production change is missing a LUCENENET comment indicating where the change (which diverges from 4.8.0) came from. Ideally, there would be a link back to the PR or commit where the code was ported from.
• 2. The name of the test method should be Pascal case. NUnit doesn't automatically detect test methods based on a naming convention, so there is no need to stick with that casing in .NET.
• 3. The test method and GetCommitData() method are not in the same order in the file as they were in Lucene. In Lucene, TestVariableSchema() (the following test in this PR) is on line 593 and TestGetCommitDataFromOldSnapshot() is on line 2064.
• 4. The original test used getLiveCommitData(), not getCommitData(). It's fine if setLiveCommitData() doesn't exist in 4.8.0, but we should LUCENENET comment to make it clear why we diverged (and that it has diverged) on each of the lines that call GetCommitData() and SetCommitData(), since these will need to be changed back when we upgrade.
• 5. The original test used newSnapshotIndexWriterConfig(null). We should port that method in LuceneTestCase rather than inlining the configuration, and add a LUCENENET comment indicating where the diverging method came from.
• 6. The TestGetCommitDataFromOldSnapshot() and GetCommitData() methods also don't have a LUCENENET comment indicating where these diverging changes came from.

[paulirwin]

@NightOwl888 My thoughts exactly, thanks for writing that all out. I'll make those changes to this PR.

[NightOwl888]

Thanks @paulirwin and @tohidemyname, this looks good to merge.