[roll] Roll infra/recipes [build] Delete unnecessary BuildResults attrs

Each of these attributes is all either:
- A constant path relative to the build directory, in which case
  computed @properties are more appropriate (attr.ib() generally
  shouldn't be used for attributes that don't need to be passed in to
  __init__).
- Tool paths that are only accessed once, in which case it's more
  consistent to inline the `GNResults.tool()` call in the place where
  the tool is accessed.

Now that we don't necessarily call `build_results.tool()` (which loads
and caches tool_paths.json) when the BuildResults object is
instantiated, the step to read tool_paths.json may appear just about
anywhere in the build depending on when `build_results.tool()` or
`gn_results.tool()` is first called. To make the step name
deterministic, eagerly load tool_paths.json when a GNResults object is
instantiated, which is the earliest possible time that the file is
guaranteed to exist.

Original-Bug: 67861
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/infra/recipes/+/513934
Original-Revision: 094fc0ee0bd5b8fbd28589f9e8c059eea475e809
GitOrigin-RevId: 371c3147401f505fbcd62c4d7f2730c8d80f1c1d
Change-Id: I1121c17ef2cd6377fa1d1cb916a5ed34c856d898