rust-revlog: make `IndexEntryBuilder` build a whole entry The `IndexEntryBuilder` we have in tests only built part of a revlog entry before this patch. It's more useful if it can build a full entry. As part of fixing that, I also added a (non-test) `IndexEntry::link_revision()`. Differential Revision: https://phab.mercurial-scm.org/D12564

[build-system]
requires = ["setuptools", "wheel"]

[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true