Add patches for directories/directories-next/option-ext

The rational is detailed in the root Cargo.toml.

While I don't personally mind MPL dependencies, even if I don't prefer them
(they're allowed in the deny.toml for a reason), I do mind the pointless scope
creep and wish to highlight how little it actually used from the crate by
re-defining it as the single function.

We could also fork directories-next, or directories, and remove the usage of
option-ext per dirs-dev/dirs-sys-rs#24, yet that'd be
a much larger task than what was done here.

In the future, it may be beneficial to submit a PR to wasmtime replacing
directories-next with home, a cargo-team maintained library to get the home
directory and associated folders. An example migration can be found at
harryfei/which-rs#80.