The code are wrapped due to us using line-length=79 before, but now some
of the code can easily fit in 88 chars.
The formatter did not change this automatically when we changed line-length,
because of magic trailing commas that gets added when they turn into multiple lines.
Black/ruff wrapping them in parens and splitting them into multiple lines
was making it difficult to read.
`data_keys` are similar to `outs`, but they provide more granularity, so we
can use them in `build_data_index` to rebuild index views with filtered
outputs. E.g. when running `dvc diff dir/file`, workspace index should only
have `dir/file` in it.
This also could be used for standalone (non-output) data in the future.
Pre-requisite for #8930
Otherwise when using brancher we end up in a strange situation where even
though we are collecting targets from `gitfs`, we are still using `localfs`
as `self.fs`, which make operations like `self.fs.abspath` in
`collect_granular` return invalid paths.
`@memoize()` memory lives as long as decorated function lives, which is
permanent in this case. Since `self` is referenced as a memory key no
`Index` will ever be freed.
Changed to use `@cached_property` whose cache lives as long as the
parent instance.