convert hex encloded account_id to AccountId instead of using zeros

[holtzman]

Motivation

In order to keep a view-onlyaccount's balances in sync with activity happening on the account outside of this instance of full-service, one can:

• use create_view_only_account_sync_request to obtain a list of txos for which the view-only account does not know the corresponding key images
• process the resulting txo_sync_request using software that has access to the account's private keys, producing a sync_view_only_account request that associates tx_out_public_keys with their corresponding key_images, and
• submit the sync_view_only_account request to the full-service with the view-only account.

The txo_sync_request generated in response to the create_view_only_account_sync_request method is supposed to include the account_id of the view-only account. This helps ensure that the tx_out_public_keys are processed with the correct account keys when generating the key_images

Prior to this PR, the account_id returned was all zeros.

In this PR

• update the response to create_view_only_account_sync_request to include the actual account_id of the view-only account, instead of generating an all-zeros placeholder account_id.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 55.60%. Comparing base (ab2af32) to head (af95b6e). Report is 194 commits behind head on main.

Files	Patch %	Lines
full-service/src/json_rpc/v2/api/wallet.rs	50.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #992 +/- ## ========================================== - Coverage 60.12% 55.60% -4.53% ========================================== Files 88 124 +36 Lines 12356 16289 +3933 Branches 2010 2799 +789 ========================================== + Hits 7429 9057 +1628 - Misses 3238 5146 +1908 - Partials 1689 2086 +397 ```

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