Reword "crate not found" resolve message

```
error[E0432]: unresolved import `some_novel_crate`
 --> file.rs:1:5
  |
1 | use some_novel_crate::Type;
  |     ^^^^^^^^^^^^^^^^ use of unresolved module or unlinked crate `some_novel_crate`
```

On resolve errors where there might be a missing crate, mention `cargo add foo`:

```
error[E0433]: failed to resolve: use of unresolved module or unlinked crate `nope`
  --> $DIR/conflicting-impl-with-err.rs:4:11
   |
LL | impl From<nope::Thing> for Error {
   |           ^^^^ use of unresolved module or unlinked crate `nope`
   |
   = help: if you wanted to use a crate named `nope`, use `cargo add nope` to add it to your `Cargo.toml`
```

2 files changed, 3 insertions, 3 deletions

diff --git a/tests/ui/tool-attributes/unknown-tool-name.rs b/tests/ui/tool-attributes/unknown-tool-name.rs
index 73fca61c65d..ba21aecc230 100644
--- a/tests/ui/tool-attributes/unknown-tool-name.rs
+++ b/tests/ui/tool-attributes/unknown-tool-name.rs
@@ -1,2 +1,2 @@
-#[foo::bar] //~ ERROR failed to resolve: use of undeclared crate or module `foo`
+#[foo::bar] //~ ERROR failed to resolve: use of unresolved module or unlinked crate `foo`
 fn main() {}
diff --git a/tests/ui/tool-attributes/unknown-tool-name.stderr b/tests/ui/tool-attributes/unknown-tool-name.stderr
index 361d359a10e..9b636fcb0bd 100644
--- a/tests/ui/tool-attributes/unknown-tool-name.stderr
+++ b/tests/ui/tool-attributes/unknown-tool-name.stderr
@@ -1,8 +1,8 @@
-error[E0433]: failed to resolve: use of undeclared crate or module `foo`
+error[E0433]: failed to resolve: use of unresolved module or unlinked crate `foo`
   --> $DIR/unknown-tool-name.rs:1:3
    |
 LL | #[foo::bar]
-   |   ^^^ use of undeclared crate or module `foo`
+   |   ^^^ use of unresolved module or unlinked crate `foo`
 
 error: aborting due to 1 previous error