feat(wallet): add view key commands

[stringhandler]

Description

Adds commands for exporting a view key and spend key for an existing wallet, and also commands for creating a read-only wallet that only has access to the view key.

Note this is only possible to the great work by @SWvheerden who enabled this functionality in the wallet.

Motivation and Context

This allows you to keep an offline cold wallet that has spend access, and at the same time listen for received funds and act on them. This enables ecommerce and exchange support without the danger of running a hot spending wallet.

How Has This Been Tested?

Tested locally

What process can a PR reviewer use to test or verify this change?

You can follow the steps in the exchange guide to use all of the additions in this PR

Breaking Changes

• [x] None
• [ ] Requires data directory on base node to be deleted
• [ ] Requires hard fork
• [ ] Other - Please specify

[github-actions[bot]]

Test Results (CI)

    3 files    123 suites   38m 48s :stopwatch: 1 300 tests 1 300 :white_check_mark: 0 :zzz: 0 :x: 3 892 runs  3 892 :white_check_mark: 0 :zzz: 0 :x:

Results for commit 6cda68e6.

:recycle: This comment has been updated with latest results.

[github-actions[bot]]

Test Results (Integration tests)

19 tests   19 :white_check_mark:  10m 54s :stopwatch:  9 suites   0 :zzz:  2 files     0 :x:  1 errors

For more details on these parsing errors, see this check.

Results for commit 6cda68e6.

:recycle: This comment has been updated with latest results.

[hansieodendaal]

I cannot get this menu to be displayed when I run the consol wallet:

        loop {
            println!("1. Create a new wallet.");
            println!("2. Recover wallet from seed words or hardware device.");
            println!("3. Create a read-only wallet using a view key.");