benchmark

[bazel] Use `includes` instead of `strip_include_prefix` (#1803)

When using `includes`, consumers will apply the headers
using `-isystem`, instead of `-I`. This will allow diagnostics
of consumers to not apply to `benchmark`.

More info:

https://bazel.build/reference/be/c-cpp#cc_library.includes

https://bazel.build/reference/be/c-cpp#cc_library.strip_include_prefix

gtest uses `includes` as well:
https://github.com/google/googletest/blob/1d17ea141d2c11b8917d2c7d029f1c4e2b9769b2/BUILD.bazel#L120