tests/lsp: move language server tests to separate folder

tests/test-sources/plugins/lsp/language-servers/ccls.nix

@@ -0,0 +1,48 @@
+{
+  example = {
+    plugins.lsp = {
+      enable = true;
+
+      servers.ccls = {
+        enable = true;
+
+        initOptions = {
+          cache = {
+            directory = ".ccls-cache";
+            format = "binary";
+            retainInMemory = 1;
+          };
+          clang = {
+            extraArgs = [];
+            excludeArgs = ["-frounding-math"];
+            pathMappings = ["/remote/>/host/"];
+            resourceDir = "";
+          };
+          client = {
+            snippetSupport = true;
+          };
+          completion = {
+            placeholder = false;
+            detailedLabel = true;
+            filterAndSort = true;
+          };
+          compilationDatabaseDirectory = "out/release";
+          diagnostics = {
+            onOpen = 0;
+            onChange = 1000;
+            onSave = 0;
+          };
+          index = {
+            threads = 0;
+            comments = 2;
+            multiVersion = 0;
+            multiVersionBlacklist = ["^/usr/include"];
+            initialBlacklist = ["."];
+            onChange = false;
+            trackDependency = 2;
+          };
+        };
+      };
+    };
+  };
+}