Add "whereis" and "get-command" to which search terms (#14797)

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# Description
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Today i saw in the general discord channel someone ask what is the
nushell equivalent of `whereis` or `get-command`. I wanted to tell the
user to use our great search via F1 but then I realized that typing in
`whereis` or `get-command` wouldn't really find you something. So I
added these two search terms.

# User-Facing Changes
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None.

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I don't think that really needs testing here :D

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crates/nu-command/src/system/which_.rs

@@ -25,7 +25,14 @@ impl Command for Which {
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["find", "path", "location", "command"]
+        vec![
+            "find",
+            "path",
+            "location",
+            "command",
+            "whereis",     // linux binary to find binary locations in path
+            "get-command", // powershell command to find commands and binaries in path
+        ]
     }
 
     fn run(