[roll] Roll fuchsia [bazel] Introduce bazel root host targets.

Bazel root host targets are Bazel targets that:

- Are built for the host build configuration only.
- Do not depend on any Ninja artifact.

As a consequence, these can be built very early in the
build with a single Ninja / Bazel invocation. And soon:

- It will be possible to build them directly with
  `fx build --host @<bazel_label>` without invoking
  Ninja at all.

- `fx build` will invoke Bazel directly to build them
  before invoking Ninja.

This CL introduces the necessary infrastructure to
support them, in particular:

- bazel_root_targets_list.gni which defines the set
  of default root host targets (currently empty) to
  build.

- //build/bazel:bazel_root_targets, a new target
  used to invoke a bazel_build_group() that can build
  all root host targets early in the build.

- bazel_tool_action() and bazel_tool_action_foreach():
  new GN templates that mimic compiled_action() and
  compiled_action_foreach(), using host binaries
  generated by Bazel.

Original-Bug: 42084668
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1269026
Original-Revision: a52b8e5564a3f2e226aa4706bab7e260a2266e29
GitOrigin-RevId: 029865720c7e5253d29a8b9dc4f71c2408a3beaf
Change-Id: I8a201e4ebc55d592f7c95a9a85db4ef7f15fd9e6