SSH widget updates when config file changes

[lauren-ciha]

Summary of the pull request

The SSH widget was not updating when the config file changed because the widget did not allow outside processes to read or write to the file.

This pull request modifies the SSHWalletWidget's FileStreamOptions to allow read/write sharing.

References and relevant issues

Resolves #2672

Detailed description of the pull request / Additional comments

Before:

• SSH widget didn't update when its config file changed
• If multiple SSH widgets pointed to the same config file, a file is busy error arose in at least one of the widgets when the config file was updated

After:

• SSH widget updates when its config file changes
• Multiple SSH widgets pointing to the same config file update together when the config file changes

Validation steps performed (locally)

• Created sample config file with two hosts
• Opened config file in text editor
• Added one (and multiple) SSH widgets to dashboard
• Repeatedly removed/added one host, saving after each change
• Found that with each save, SSH widget updated to reflect the config file

PR checklist

• Closes SSH widget does not reflect changes to the content of the configured config file #2672
• Tests added/passed
• Documentation updated