⚡ (setVariable) Add "Environment name" value in Set variable block (#850)

Closes #848
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
### Summary by CodeRabbit

- New Feature: Added "Environment name" as a new value type in the
SetVariable function, allowing users to distinguish between 'web' and
'whatsapp' environments.
- Refactor: Simplified session state handling in `resumeWhatsAppFlow.ts`
for improved code clarity.
- Refactor: Updated `startWhatsAppSession.ts` to include an initial
session state with WhatsApp contact and expiry timeout, enhancing
session management.
- Bug Fix: Improved null handling in `executeSetVariable.ts` for
'Contact name' and 'Phone number', preventing potential issues with
falsy values.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/builder/src/features/blocks/logic/setVariable/components/SetVariableContent.tsx

@@ -62,6 +62,7 @@ const Expression = ({
     case 'Tomorrow':
     case 'User ID':
     case 'Moment of the day':
+    case 'Environment name':
     case 'Yesterday': {
       return (
         <Text as="span">

apps/builder/src/features/blocks/logic/setVariable/components/SetVariableSettings.tsx

@@ -158,6 +158,17 @@ const SetVariableValue = ({
         </Alert>
       )
     }
+    case 'Environment name': {
+      return (
+        <Alert fontSize="sm">
+          <AlertIcon />
+          <Text>
+            Will return either <Tag size="sm">web</Tag> or{' '}
+            <Tag size="sm">whatsapp</Tag>.
+          </Text>
+        </Alert>
+      )
+    }
     case 'Contact name':
     case 'Phone number':
     case 'Random ID':