chore: new Cargo feature all-static

This is primarily for the release process of rust-lang/rust.

Note that in rustc-worksace-hack[1] it enable http2 via libnghttp2,
cargo probably needs to enable it to compile in rust-lang/rust.

[1]: https://github.com/rust-lang/rust/blob/992d154f3a84cc8abcefcf6e6cf3698e4821b506/src/tools/rustc-workspace-hack/Cargo.toml#L77

Co-authored-by: Scott Schafer <schaferjscott@gmail.com>
Co-authored-by: Eric Huss <eric@huss.org>

Author: 3 people

Cargo.toml

@@ -139,3 +139,5 @@ doc = false
 vendored-openssl = ["openssl/vendored"]
 vendored-libgit2 = ["libgit2-sys/vendored"]
 pretty-env-logger = ["pretty_env_logger"]
+# This is primarily used by rust-lang/rust distributing cargo the executable.
+all-static = ['vendored-openssl', 'curl/static-curl', 'curl/http2', 'curl/force-system-lib-on-osx']