fix: Improve Dropdown component handling of custom values and add regression test (#7486)

* ✨ (frontend): Add handleOnNewValue prop to Dropdown component to allow selecting a value not in the list
🔧 (frontend): Remove TODO comment and keep handleOnNewValue prop in DropdownComponent
✅ (frontend): Add test for selecting a value not in the list in Dropdown component

* 🐛 (dropdownComponent/index.tsx): fix issue where custom value was not being added to validOptions and filteredOptions when pressing Enter
✨ (dropdownComponent/index.tsx): improve functionality to reset filtered options and custom value input when opening the dropdown

* 🔧 (dropdownComponent/index.tsx): improve styling and layout of dropdown component for better user experience

* ♻️ (dropdownComponent/index.tsx): remove unnecessary comments and improve code readability by removing redundant comments and separating render helper functions from logic blocks.

* 📝 (dropdownComponent/index.tsx): add 'no-focus-visible' class to dropdown component to remove focus outline for better accessibility
📝 (applies.css): add styles for 'no-focus-visible' class to remove focus outline for better accessibility

src/frontend/tests/extended/regression/general-bugs-dropdown-select-not-in-list.spec.ts

@@ -0,0 +1,44 @@
+import { expect, test } from "@playwright/test";
+import { awaitBootstrapTest } from "../../utils/await-bootstrap-test";
+
+test(
+  "user must be able to select a value from dropdown that is not in the list",
+  { tag: ["@release", "@components"] },
+  async ({ page }) => {
+    await awaitBootstrapTest(page);
+
+    await page.waitForSelector('[data-testid="blank-flow"]', {
+      timeout: 30000,
+    });
+    await page.getByTestId("blank-flow").click();
+    await page.getByTestId("sidebar-search-input").click();
+    await page.getByTestId("sidebar-search-input").fill("openai");
+
+    await page.waitForSelector('[data-testid="modelsOpenAI"]', {
+      timeout: 1000,
+    });
+
+    await page
+      .getByTestId("modelsOpenAI")
+      .hover()
+      .then(async () => {
+        await page.getByTestId("add-component-button-openai").last().click();
+      });
+
+    await page.getByTestId("fit_view").click();
+
+    await page.getByTestId("dropdown_str_model_name").click();
+    await page.getByTestId("dropdown_search_input").click();
+    await page
+      .getByTestId("dropdown_search_input")
+      .fill("this is a test langflow");
+    await page.keyboard.press("Enter");
+
+    await page.waitForTimeout(500);
+
+    const value = await page
+      .getByTestId("value-dropdown-dropdown_str_model_name")
+      .textContent();
+    expect(value?.trim()).toBe("this is a test langflow");
+  },
+);