Support Organisation-Level Audit Log Records

Currently the platform only supports Audit Log records at the project level or below. We should modify this to support events at the Organisation-Level.

There is a list of items that we want to be able to track, but we should focus on implementing a small number of these as a PoC for organisation-level records. These items are separated into specific sub-issues of this parent issue.

Suggestion would be to complete [this task](https://github.com/Flagsmith/flagsmith/issues/7571) as a PoC for these events.

The scope of this work is to extend the `AuditLog` model to add a new `organisation` field, update the existing and/or add new API endpoints for retrieving Audit Log records to retrieve them for an organisation, and to add a new Audit Log view in the dashboard at the Organisation level. The endpoint that lists the audit log records for the organisation should include all audit log records for all projects and environments inside the organisation. It should be possible to filter by project and subsequently environment (see usage page for an example of this filtering functionality). Users must be organisation admin to retrieve the organisation level audit logs.