[bazel] Improve runfiles handling (#10098)

we can't use runfiles directory on Windows due to path lengths, so swap
to manifest strategy. Parsing the manifest is a bit complex and the
format is changing in Bazel upstream, so pull in the official Rust
library (via a small hack to make it importable...) and cleanup all the
associated logic to work cleanly in both bazel and cargo without extra
confusion

BUILD.bazel

@@ -1,3 +1,7 @@
+load("@apple_support//xcode:xcode_config.bzl", "xcode_config")
+
+xcode_config(name = "disable_xcode")
+
 # We mark the local platform as glibc-compatible so that rust can grab a toolchain for us.
 # TODO(zbarsky): Upstream a better libc constraint into rules_rust.
 # We only enable this on linux though for sanity, and because it breaks remote execution.