crates_repository fails if a workspace contains . as a member

[illicitonion]

This Cargo.toml:

[workspace]

members = [
  ".",
  "hello-lib",
]

[package]
name = "hello-rust"
version = "0.1.0"
edition = "2018"

[dependencies]
hello-lib = { path = "hello-lib" }
hex = "0.4.2"

currently fails to generate a repository because of this error:

Error: Some manifests are not being tracked. Please add the following labels to the `manifests` key: {
    "//package:Cargo.toml",
}

where package is the package containing the above Cargo.toml.

We should do the path normalisation to absolute paths before filtering, and normalise out any /./ or /../ path segments too.