Update CHANGELOG.md for v5.0.0

[tfenne]

Expands the existing 5.0.0 stub (which previously covered only the CRAM 3.1 write work) into a complete entry covering everything since 4.3.0.

Adds:

• Lead headlines summarizing the major themes (CRAM 3.1 writing, slimmer runtime deps, faster BAM [de]compression, enforced formatting, fixed test reporting).
• A prominent ⚠️ Breaking changes section calling out SRA removal, Nashorn now opt-in, the SAMRecord.toString() format change, the removed CRAM slice digest tags, and the new default CRAM version 3.1.
• A new "CRAM correctness and cross-implementation fixes" section consolidating the read- and write-path fixes that improve interop with samtools/htslib (TLEN computation, CIGAR =/X comparison, CIGAR reconstruction for sequence '*', container-with-no-slices crash, archive header overflow, unmapped-read query, supplementary/secondary read-name limitation).
• Performance entries beyond just the CRAM-internal optimizations: jlibdeflate integration, the BAM decoding path improvements, and a long-read-friendly bases-per-slice threshold.
• A bug-fix section covering the LTF8 9-byte write fix, the SamLocusIterator offset bug, the SamPairUtil dovetail fix, and the snappy native-load UnsatisfiedLinkError catch.
• A build, tooling, and dependency clean-up section: Palantir Java Format + Spotless enforcement, Maven Central portal migration, snapshot version naming, deprecation cleanup, the test-runner pass/fail-reporting fix, and the dependency clean-up (commons-logging constraint, Nashorn compileOnly, ngs-java removal).
• A compatibility line noting JDK 17 / 21 / 24 spot-checks.
• Expanded testing entries: the hts-specs CRAM 3.0/3.1 compliance tests, FQZComp round-trip tests, CRAI correctness tests, test-suite speedups, the CEUTrio test-data downsizing, and the JS filter test bulk-up.