fix: inconsistent behavior with multiple invocations of SwaggerUI (via #4923)

* add narrow e2e tests
* add failing system unit test
* break plugin object inheritance in combinePlugins
* style: add braces to if block
* drop unused `lodash.repeat` import
* remove deep-freeze from lockfile

test/e2e-cypress/tests/bugs/4865.js

@@ -0,0 +1,19 @@
+describe("#4865: multiple invocations + OAS3 plugin", () => {
+  it("control: should render the OAS3 badge correctly", () => {
+    // This is a sanity check to make sure the badge is present.
+    // If this is failing, it's probably not related to #4865.
+    cy.visit("/?url=/documents/petstore-expanded.openapi.yaml")
+      .get("#swagger-ui")
+      .get("pre.version")
+      .contains("OAS3")
+  })
+
+  it("test: should render the OAS3 badge correctly after re-initializing the UI", () => {
+    cy.visit("/?url=/documents/petstore-expanded.openapi.yaml")
+      .window()
+      .then(win => win.onload()) // re-initializes Swagger UI
+      .get("#swagger-ui")
+      .get("pre.version")
+      .contains("OAS3")
+  })
+})