Add tests making sure linter integrate with program diagnostics (#2208)

Those tests were missing and because the rule tester runs outside of the
program flow you can't test diagnostics in there. So adding those tests
to make sure this work when integrated

common/changes/@typespec/compiler/test-linter-integration_2023-07-25-00-15.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@typespec/compiler",
+      "comment": "",
+      "type": "none"
+    }
+  ],
+  "packageName": "@typespec/compiler"
+}

packages/compiler/test/core/linter.test.ts

@@ -209,4 +209,43 @@ describe("compiler: linter", () => {
       expectDiagnosticEmpty(linter.lint());
     });
   });
+
+  describe("(integration) loading in program", () => {
+    async function diagnoseReal(code: string) {
+      const host = await createTestHost();
+      host.addTypeSpecFile("main.tsp", code);
+      host.addTypeSpecFile(
+        "node_modules/my-lib/package.json",
+        JSON.stringify({ name: "my-lib", main: "index.js" })
+      );
+      host.addJsFile("node_modules/my-lib/index.js", {
+        $lib: createTypeSpecLibrary({
+          name: "my-lib",
+          diagnostics: {},
+          linter: { rules: [noModelFoo] },
+        }),
+      });
+
+      return await host.diagnose("main.tsp", {
+        linterRuleSet: {
+          enable: { "my-lib/no-model-foo": true },
+        },
+      });
+    }
+
+    it("emit diagnostic when rule report", async () => {
+      const diagnostics = await diagnoseReal(`
+      model Foo {}`);
+
+      expectDiagnostics(diagnostics, { code: "my-lib/no-model-foo" });
+    });
+
+    it("doesn't emit diagnostic when suppressed", async () => {
+      const diagnostics = await diagnoseReal(`
+      #suppress "my-lib/no-model-foo"
+      model Foo {}`);
+
+      expectDiagnosticEmpty(diagnostics);
+    });
+  });
 });