[roll] Roll fuchsia [bazel] Add //build/bazel/host_tests:host_tests

This target will be the root of all dependencies to host tests
in the Bazel graph that will be visible to `fx test` and infra
test runners. For now, this just points to the simple C++ and
Python host tests that currently exist in the tree.

When adding new Bazel host tests, their label, or that of a
corresponding test_suite() should be added to the `tests`
list for the //build/bazel/host_tests test_suite() target.

For now, this can be manually tested with:

```
fx bazel test --config=host //build/bazel/host_tests
```

Which will run all the tests properly, or

```
python3 build/bazel/scripts/export_host_tests.py list //build/bazel/host_tests
```

Which generates a `tests.json` file with entries for all host tests.

Note that support for running host tests directly with
`fx bazel test --config=host ...` is purely experimental and might not
be guaranteed to work in the future. `fx test --host ...` will remain
the official way to run Bazel host tests locally, but the plumbing
to do that will appear in future CLs. This is only one step towards
this.

Original-Bug: 349341932
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1504897
Original-Revision: f3966c5b004181e2485efd1089d15f07b7651c6a
GitOrigin-RevId: f73f60bd1711461932f83b6366f9606974ae29d2
Change-Id: I9186635ceae1a7fa44fba489dadec542376e8225