HCD-209: Fix queries on early-open BTI files

[blambov]

What is the issue

HCD-209

Early open SSTables created when an sstable is complete, but the whole compaction isn't, were not properly set up because of a missing updateFileHandle call in openFinalEarly.

What does this PR fix and why was it fixed

Add the missing update and changes updateFileHandle to also take care of the file length to clarify all file handle updates.

Also includes fix for CASSANDRA-20976 (partially-built indexes were not properly copied with sharedCopy).

[github-actions]

Checklist before you submit for review

• This PR adheres to the Definition of Done
• Make sure there is a PR in the CNDB project updating the Converged Cassandra version
• Use NoSpamLogger for log lines that may appear frequently in the logs
• Verify test results on Butler
• Test coverage for new/modified code is > 80%
• Proper code formatting
• Proper title for each commit staring with the project-issue number, like CNDB-1234
• Each commit has a meaningful description
• Each commit is not very long and contains related changes
• Renames, moves and reformatting are in distinct commits
• All new files should contain the DataStax copyright header instead of the Apache License one

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
82.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cassci-bot]

❌ Build ds-cassandra-pr-gate/PR-2068 rejected by Butler

---

1 regressions found
See build details here

---

Found 1 new test failures

Test	Explanation	Runs	Upstream
o.a.c.index.sai.cql.VectorKeyRestrictedOnPartitionTest.partitionRestrictedWidePartitionBqCompressedTest[db] (compression)	REGRESSION	🔴🔵	0 / 10

---

Found 8 known test failures