feat: convert soft_limit to limit (#22048)

In relation to
[`internal#1281`](https://github.com/coder/internal/issues/1281)

Remove the `soft_limit` field from the `Feature` type and simplify
license limit handling. This change:

- Removes the `soft_limit` field from the API and SDK
- Uses the soft limit value as the single `limit` value in the UI and
API
- Simplifies warning logic to only show warnings when the limit is
exceeded
- Updates tests to reflect the new behavior
- Updates the UI to use the single limit value for display

enterprise/coderd/coderd_test.go

@@ -678,7 +678,7 @@ func TestManagedAgentLimit(t *testing.T) {
 			// expiry warnings.
 			GraceAt:   time.Now().Add(time.Hour * 24 * 60),
 			ExpiresAt: time.Now().Add(time.Hour * 24 * 90),
-		}).ManagedAgentLimit(1, 1),
+		}).ManagedAgentLimit(1),
 	})
 
 	// Get entitlements to check that the license is a-ok.
@@ -689,11 +689,7 @@ func TestManagedAgentLimit(t *testing.T) {
 	require.True(t, agentLimit.Enabled)
 	require.NotNil(t, agentLimit.Limit)
 	require.EqualValues(t, 1, *agentLimit.Limit)
-	require.NotNil(t, agentLimit.SoftLimit)
-	require.EqualValues(t, 1, *agentLimit.SoftLimit)
 	require.Empty(t, sdkEntitlements.Errors)
-	// There should be a warning since we're really close to our agent limit.
-	require.Equal(t, sdkEntitlements.Warnings[0], "You are approaching the managed agent limit in your license. Please refer to the Deployment Licenses page for more information.")
 
 	// Create a fake provision response that claims there are agents in the
 	// template and every built workspace.