docs: DX and performance improvements in API reference (#9430)

- Improve scroll behavior between active sections
- Improve lag when clicking on a sidebar item
- Refactor internal working of the `SidebarProvider` to find active items faster.
- Use Next.js's `useRouter` hook for changing the hash (since they added the option to disable scroll)
- Change `isBrowser` from a hook to a provider since it's widely used across applications.
- Other general improvements and fixes.

Closes DOCS-952

www/packages/docs-ui/src/providers/LearningPath/index.tsx

@@ -1,10 +1,9 @@
 "use client"
 
-import { useIsBrowser } from "@/hooks"
 import { getLearningPath } from "@/utils/learning-paths"
 import React, { createContext, useContext, useEffect, useState } from "react"
 import { LearningPathFinishType } from "@/components/LearningPath/Finish"
-import { useAnalytics } from "docs-ui"
+import { useAnalytics, useIsBrowser } from "docs-ui"
 import { usePathname, useRouter } from "next/navigation"
 
 export type LearningPathType = {
@@ -54,7 +53,7 @@ export const LearningPathProvider: React.FC<LearningPathProviderProps> = ({
 }) => {
   const [path, setPath] = useState<LearningPathType | null>(null)
   const [currentStep, setCurrentStep] = useState(-1)
-  const isBrowser = useIsBrowser()
+  const { isBrowser } = useIsBrowser()
   const pathname = usePathname()
   const router = useRouter()
   const { track } = useAnalytics()