[native] Update height calculations for SIWEPanel

Summary:
Two changes here:

1. I updated the manually-determined offsets we use for the WalletConnect modal height. I did this by playing around with the modal and picking numbers that made it look good.
2. I added some consideration for the keyboard height, since it's possible to search the WalletConnect modal. To achieve this, I had to introduce a new useKeyboardHeight hook.

Depends on D9436

Test Plan:
I tested the WalletConnect modal:

1. Tested iOS and Android physical devices
2. Tested in a public staging environment (comm.domains)
3. Tested the QR code scan feature on web
4. Tested expanding to see "All wallets"
5. Tested selecting a wallet (Rainbow)
6. Tested searching for a wallet by typing a query

Some videos of the testing can be seen in the final diff in the stack.

Reviewers: rohan, atul, ginsu

Reviewed By: ginsu

Subscribers: tomek, wyilio

Differential Revision: https://phab.comm.dev/D9437