Rename GraphQL field `hasSolutions` to `hasRemediations` on `vulnerabilities`

The GraphQL field hasSolutions on vulnerabilities has caused confusion with a customer (internal Slack link - 2023-06-09) because its name is misleading.

Vulnerabilities::Finding has a field named solutions, and the value of this field is shown under the Solution section when viewing a vulnerability on the web.

The hasSolutions field however does not check this field. Instead it checks if the Vulnerabilities::Finding has any related Vulnerabilities::Remediation records.

To make this clearer we should rename hasSolutions to hasRemediations.

While debugging this it was noted that the field often returns null rather than false. We should fix the method to more reliably return a boolean while we are touching this code.

Proposed solution

• Add a new field hasRemediations to the vulnerabilities GraphQL type with exactly the same behaviour as hasSolutions
• Deprecate hasSolutions
• Update front end and any other calling code to use the new field
• Make both fields more reliably return false rather than null