wallet_addEthereumChain should ask users to switch chain after the network is successfully added

[darkdh]

In https://docs.metamask.io/guide/rpc-api.html#other-rpc-methods
The user may choose to switch to the chain once it has been added.

So our behavior difference is revealed on https://cryptomeda.tech/

STR/Cases:

Found via brave/brave-core#10939

Test plan

1. Setup wallet
2. Navigate to https://cryptomeda.tech/
3. Click "Connect Wallet"
4. Approve add network request
5. After network is added, there will be a prompt to switch to network just added
6. Approve switch network request
7. The wallet should be on Polygon network

[srirambv]

Brave	1.32.113 Chromium: 96.0.4664.45 (Official Build) (64-bit)
Revision	76e4c1bb2ab4671b8beba3444e61c0f17584b2fc-refs/branch-heads/4664@{#947}
OS	☑️ Linux	☑️ Windows 11 Version Dev (Build 22504.1010)	☑️ macOS Version 12.0.1 (Build 21A559)
Verified steps from issue description but used local test page Verified switch network prompt is shown immediately after adding the new network chain to the list
	19291.-.Linux.mp4	19291.-.Windows.mov	19291.-.macOS.mov