Update online_event_template to use workflow message

This updates the default online event template to use the variables assigned by
the workflow template

This works to standardise the variables previously in dataArray
, lineItem, totalAmount, taxAmount to reflect the
approach in other templates per
https://docs.civicrm.org/user/en/latest/email/message-templates/#variables-and-tokens-in-workflow-message-templates

However, for participants, per the helpful discussion at
#24576

the expectation is that the primaryParticipant gets the values for
all participants whereas the others only get line items,
tax breakdowns, totals that relate to them.

Hence I have assigned an array participants that holds detials for all participants
and the template iterates through them showing all or just the
one that relates to the assigned participant id depending on
whether it is primary.

This allows the template to display in the Message preview and should
also mean that those values that I have addressed will always reflect
the participantID being used. This also addresses some notices
and incompatibility with secure smarty.

However, there are still values I haven't made sense of, or otherwise left
out of the scope of this PR in the template.

Also note I updated the taxBreakdown in the contribution trait - I decided it
was cloberring the amount as it iterated through the line items - rather than
doing a running total.

CRM/Contribute/WorkflowMessage/ContributionTrait.php

@@ -147,11 +147,20 @@ public function getTaxRateBreakdown(): array {
     }
     $this->taxRateBreakdown = [];
     foreach ($this->getLineItems() as $lineItem) {
-      $this->taxRateBreakdown[$lineItem['tax_rate']] = [
-        'amount' => $lineItem['tax_amount'] ?? 0,
-        'rate' => $lineItem['tax_rate'],
-        'percentage' => sprintf('%.2f', $lineItem['tax_rate']),
-      ];
+      if (!isset($this->taxRateBreakdown[$lineItem['tax_rate']])) {
+        $this->taxRateBreakdown[$lineItem['tax_rate']] = [
+          'amount' => 0,
+          'rate' => $lineItem['tax_rate'],
+          'percentage' => sprintf('%.2f', $lineItem['tax_rate']),
+        ];
+      }
+      $this->taxRateBreakdown[$lineItem['tax_rate']]['amount'] += $lineItem['tax_amount'] ?? 0;
+    }
+    // Remove the rates with no value.
+    foreach ($this->taxRateBreakdown as $rate => $details) {
+      if ($details['amount'] === 0.0) {
+        unset($this->taxRateBreakdown[$rate]);
+      }
     }
     if (array_keys($this->taxRateBreakdown) === [0]) {
       // If the only tax rate charged is 0% then no tax breakdown is returned.