chore: add db query to retrieve workspaces & their agents (#14792)

Second PR for #14716.

Adds a query that, given a user ID, returns all the workspaces they own, that can also be `ActionRead` by the requesting user.

```
type GetWorkspacesAndAgentsByOwnerIDRow struct {
	WorkspaceID      uuid.UUID            `db:"workspace_id" json:"workspace_id"`
	WorkspaceName    string               `db:"workspace_name" json:"workspace_name"`
	JobStatus        ProvisionerJobStatus `db:"job_status" json:"job_status"`
	Transition       WorkspaceTransition  `db:"transition" json:"transition"`
	Agents           []AgentIDNamePair    `db:"agents" json:"agents"`
}
```
 `JobStatus` and `Transition` are set using the latest build/job of the workspace. Deleted workspaces are not included.

coderd/database/dbmem/dbmem.go

@@ -6839,6 +6839,11 @@ func (q *FakeQuerier) GetWorkspaces(ctx context.Context, arg database.GetWorkspa
 	return workspaceRows, err
 }
 
+func (q *FakeQuerier) GetWorkspacesAndAgentsByOwnerID(ctx context.Context, ownerID uuid.UUID) ([]database.GetWorkspacesAndAgentsByOwnerIDRow, error) {
+	// No auth filter.
+	return q.GetAuthorizedWorkspacesAndAgentsByOwnerID(ctx, ownerID, nil)
+}
+
 func (q *FakeQuerier) GetWorkspacesEligibleForTransition(ctx context.Context, now time.Time) ([]database.WorkspaceTable, error) {
 	q.mutex.RLock()
 	defer q.mutex.RUnlock()
@@ -11224,6 +11229,67 @@ func (q *FakeQuerier) GetAuthorizedWorkspaces(ctx context.Context, arg database.
 	return q.convertToWorkspaceRowsNoLock(ctx, workspaces, int64(beforePageCount), arg.WithSummary), nil
 }
 
+func (q *FakeQuerier) GetAuthorizedWorkspacesAndAgentsByOwnerID(ctx context.Context, ownerID uuid.UUID, prepared rbac.PreparedAuthorized) ([]database.GetWorkspacesAndAgentsByOwnerIDRow, error) {
+	q.mutex.RLock()
+	defer q.mutex.RUnlock()
+
+	if prepared != nil {
+		// Call this to match the same function calls as the SQL implementation.
+		_, err := prepared.CompileToSQL(ctx, rbac.ConfigWithoutACL())
+		if err != nil {
+			return nil, err
+		}
+	}
+	workspaces := make([]database.WorkspaceTable, 0)
+	for _, workspace := range q.workspaces {
+		if workspace.OwnerID == ownerID && !workspace.Deleted {
+			workspaces = append(workspaces, workspace)
+		}
+	}
+
+	out := make([]database.GetWorkspacesAndAgentsByOwnerIDRow, 0, len(workspaces))
+	for _, w := range workspaces {
+		// these always exist
+		build, err := q.getLatestWorkspaceBuildByWorkspaceIDNoLock(ctx, w.ID)
+		if err != nil {
+			return nil, xerrors.Errorf("get latest build: %w", err)
+		}
+
+		job, err := q.getProvisionerJobByIDNoLock(ctx, build.JobID)
+		if err != nil {
+			return nil, xerrors.Errorf("get provisioner job: %w", err)
+		}
+
+		outAgents := make([]database.AgentIDNamePair, 0)
+		resources, err := q.getWorkspaceResourcesByJobIDNoLock(ctx, job.ID)
+		if err != nil {
+			return nil, xerrors.Errorf("get workspace resources: %w", err)
+		}
+		if len(resources) > 0 {
+			agents, err := q.getWorkspaceAgentsByResourceIDsNoLock(ctx, []uuid.UUID{resources[0].ID})
+			if err != nil {
+				return nil, xerrors.Errorf("get workspace agents: %w", err)
+			}
+			for _, a := range agents {
+				outAgents = append(outAgents, database.AgentIDNamePair{
+					ID:   a.ID,
+					Name: a.Name,
+				})
+			}
+		}
+
+		out = append(out, database.GetWorkspacesAndAgentsByOwnerIDRow{
+			ID:         w.ID,
+			Name:       w.Name,
+			JobStatus:  job.JobStatus,
+			Transition: build.Transition,
+			Agents:     outAgents,
+		})
+	}
+
+	return out, nil
+}
+
 func (q *FakeQuerier) GetAuthorizedUsers(ctx context.Context, arg database.GetUsersParams, prepared rbac.PreparedAuthorized) ([]database.GetUsersRow, error) {
 	if err := validateDatabaseType(arg); err != nil {
 		return nil, err