qa: Port RPC tests to Python 3, add comprehensive test runner
Migrate all 92 Python files in qa/ from Python 2 to Python 3:
- Update shebangs from python2 to python3
- Replace print statements with print() calls
- Fix imports (http.client, urllib.parse, queue, io, functools)
- Convert xrange→range, 0L→0, long→int, cmp→key functions
- Fix except/as syntax, bytes/str handling, integer division
- Use relative imports in test_framework/ package
Add qa/run-tests.sh: multi-stage test runner (1183 lines)
- Stage 1: Build/binary verification
- Stage 2: Security hardening (PIE, NX, RELRO, canary, FORTIFY)
- Stage 3-4: Boost/Google test binaries
- Stage 5: Library tests (secp256k1, univalue)
- Stage 6: RandomX validation (live chain mining + block checks)
- Stage 7: RPC integration (skipped: regtest mining incompatible)
- Stage 8: Source code invariant checks
- Stage 8b: DragonX-specific source checks (11 tests)
- Flags: --chain=dragonx, --live-dragonx, --save-release, --quick
- Timestamped reports with release archiving to qa/release-reports/
Add qa/clean-test-reports.sh for housekeeping (--keep=N, --dry-run)
Fix test build infrastructure:
- src/Makefile.gtest.include: fix zcash_gtest→hush_gtest refs,
remove 17 stale source files, add LIBZCASH/LIBHUSH/LIBRANDOMX
- src/Makefile.test.include: remove stale sources, deduplicate
LDADD/CXXFLAGS, add missing libraries
- src/gtest/test_checkblock.cpp: add height param to ContextualCheckBlock
- src/test/test_bitcoin.cpp: remove JoinSplitTestingSetup (dead code)
Add qa/test-reports/ to .gitignore for transient output.
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