Allow using the `rescan` option in settings, even with a remote node without owner key

[dbadol]

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Bug description When using a remote node, the rescan option in settings is greyed out. However, as shown in https://github.com/BeamMW/beam/issues/1963, it seems that a rescan is still possible even with a remote node without owner key.

To Reproduce Steps to reproduce the behaviour:

1. Open the GUI wallet
2. Go to Settings and set a remote node
3. Go to Settings / Utilities
4. See that the rescan option is greyed out

Current behaviour The user cannot even attempt a rescan when using a remote node.

Expected behaviour If the rescan is indeed possible with remote nodes without owner key (see https://github.com/BeamMW/beam/issues/1963) then the rescan option in the GUI should remain available, even for remote nodes. In case the remote node does not have the owner key, a message could be displayed to explain that the process will take time and will download data to perform the rescan.

Platform and build

• Tested on Windows 10 22H2
• BEAM Build number 7.5.13840

Screenshot

[dbadol]

If possible, the rescan process (which is long when the remote node does not have the owner key) should be done in background. Maybe with an progress message at the top of the wallet (like for the integrated node sync).