[fly1d]

Fixes #585.

Requesting an etree builder with fullTree=False, then True, then False returns a new class for the first configuration. Cache misses test literal keys while initializing the module and argument buckets, discarding previously cached configurations. A parser built with the earlier class can then fail an isinstance check against the class obtained again.

Preserve those buckets when inserting a new configuration, and remove the redundant intermediate entry. Add factory and public tree-builder regressions, a changelog entry and author attribution.

Validation on Python 3.11.16/macOS arm64, using local setuptools==70.3.0 build/test constraints:

• The seven new cases produce six failures and one pass on unchanged main; all seven pass with the fix.
• Tox py311-base: 17506 passed, 15885 skipped, 683 xfailed; flake8 passed.
• Tox py311-optional with chardet==5.2.0: 23570 passed, 6038 skipped, 1017 xfailed; flake8 passed.

The setuptools constraint avoids the existing pkg_resources packaging failure. With current optional dependencies (chardet==7.7.0), test_char_win1252 fails on both this branch and unchanged main. These are local compatibility constraints; repository requirements and test configuration are unchanged.

AppVeyor 1.0.452: py27-base passed (22183 passed, 10874 skipped, 1017 xfailed), including flake8. The other jobs stop before tests: the launcher cannot find Python 3.7, and the Python 2.7 optional environment cannot build lxml without Visual C++ 9.0. The same setup failures appear in the preceding 1.0.451 build.