feat(rust): Support new rust-toolchain format (#1938)

* feat(rust): Support new rust-toolchain format

* Match file parsing with rustup and update link

* Use cargo to deserialize the rust-toolchain file

* Filter empty channel strings after extraction

* Use the option value instead of rewrapping

Cargo.lock

@@ -1122,18 +1122,18 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.116"
+version = "1.0.117"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96fe57af81d28386a513cbc6858332abc6117cfdb5999647c6444b8f43a370a5"
+checksum = "b88fa983de7720629c9387e9f517353ed404164b1e482c970a90c1a4aaf7dc1a"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.116"
+version = "1.0.117"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f630a6370fd8e457873b4bd2ffdae75408bc291ba72be773772a4c2a065d9ae8"
+checksum = "cbd1ae72adb44aab48f325a02444a5fc079349a8d804c1fc922aed3f7454c74e"
 dependencies = [
  "proc-macro2",
  "quote 1.0.7",
@@ -1210,7 +1210,7 @@ dependencies = [
  "rayon",
  "regex",
  "rust-ini",
- "serde_derive",
+ "serde",
  "serde_json",
  "shell-words",
  "starship_module_config_derive",