ssh: Lookup language servers in env on SSH host (#17658)

Release Notes:

- ssh remoting: Lookup language server binaries in environment on SSH
host

---------

Co-authored-by: Bennet <bennet@zed.dev>

crates/proto/proto/zed.proto

@@ -283,7 +283,13 @@ message Envelope {
         CloseBuffer close_buffer = 245;
         UpdateUserSettings update_user_settings = 246;
 
-        CreateLanguageServer create_language_server = 247; // current max
+        CreateLanguageServer create_language_server = 247;
+
+        WhichCommand which_command = 248;
+        WhichCommandResponse which_command_response = 249;
+
+        ShellEnv shell_env = 250;
+        ShellEnvResponse shell_env_response = 251; // current max
     }
 
     reserved 158 to 161;
@@ -2503,6 +2509,7 @@ message UpdateUserSettings {
 message LanguageServerCommand {
    string path = 1;
    repeated string arguments = 2;
+   map<string, string> env = 3;
 }
 
 message AvailableLanguage {
@@ -2522,6 +2529,25 @@ message CreateLanguageServer {
     AvailableLanguage language = 7;
 }
 
+message WhichCommand {
+    uint64 project_id = 1;
+    uint64 worktree_id = 2;
+    string command = 3;
+}
+
+message WhichCommandResponse {
+    optional string path = 1;
+}
+
+message ShellEnv {
+    uint64 project_id = 1;
+    uint64 worktree_id = 2;
+}
+
+message ShellEnvResponse {
+    map<string, string> env = 1;
+}
+
 // message RestartLanguageServer {
 
 // }

crates/proto/src/proto.rs

@@ -367,7 +367,11 @@ messages!(
     (FindSearchCandidatesResponse, Background),
     (CloseBuffer, Foreground),
     (UpdateUserSettings, Foreground),
-    (CreateLanguageServer, Foreground)
+    (CreateLanguageServer, Foreground),
+    (WhichCommand, Foreground),
+    (WhichCommandResponse, Foreground),
+    (ShellEnv, Foreground),
+    (ShellEnvResponse, Foreground),
 );
 
 request_messages!(
@@ -491,7 +495,9 @@ request_messages!(
     (SynchronizeContexts, SynchronizeContextsResponse),
     (LspExtSwitchSourceHeader, LspExtSwitchSourceHeaderResponse),
     (AddWorktree, AddWorktreeResponse),
-    (CreateLanguageServer, Ack)
+    (CreateLanguageServer, Ack),
+    (WhichCommand, WhichCommandResponse),
+    (ShellEnv, ShellEnvResponse)
 );
 
 entity_messages!(
@@ -565,7 +571,9 @@ entity_messages!(
     SynchronizeContexts,
     LspExtSwitchSourceHeader,
     UpdateUserSettings,
-    CreateLanguageServer
+    CreateLanguageServer,
+    WhichCommand,
+    ShellEnv
 );
 
 entity_messages!(