Wallet: NFT improvement on importing

[nuo-xu]

Some users from the community gave us some feedback that it's a bit hard to import NFTs in our Wallet.
We agree that there is some improvement we can do on this topic.

1. long press on each NFT grid to hide NFT
2. adding a + button in NFT tab for users to click which will open Add custom asset screen
3. In the Add custom asset screen, move token's contract address on top of the form like what desktop has.

[srirambv]

Verification passed on the following devices running 1.53 (23.7.6.16)

• Verified steps from issue description and #7563
• Verified long press on NFT shows the hide button
• Verified able to hide and show NFTs
• Verified clicking on + on NFT tab brings up the add custom token prompt
• Verified Token Address is set at the top of the add custom token on Add NFT screen

iPhone 7+ (iOS 15.7.3)	iPhone 13 (iOS 16.5)	iPad Pro (iOS 16.6 Beta)
7556-iPhone.7+.MP4	7556-iPhone.13.MP4	7556-iPad.Pro.MP4