fix: fixed handling of how and when to set ALL option (SigNoz#7244)

Author: SagarRajput-7

frontend/src/container/NewDashboard/DashboardVariablesSelection/VariableItem.tsx

@@ -157,6 +157,13 @@ function VariableItem({
 								} else {
 									[value] = newOptionsData;
 								}
+							} else if (variableData.multiSelect) {
+								const { selectedValue } = variableData;
+								allSelected =
+									newOptionsData.length > 0 &&
+									Array.isArray(selectedValue) &&
+									selectedValue.length === newOptionsData.length &&
+									newOptionsData.every((option) => selectedValue.includes(option));
 							}
 
 							if (variableData && variableData?.name && variableData?.id) {
@@ -235,8 +242,9 @@ function VariableItem({
 		},
 	);
 
-	const handleChange = (value: string | string[]): void => {
-		// if value is equal to selected value then return
+	const handleChange = (inputValue: string | string[]): void => {
+		const value = variableData.multiSelect && !inputValue ? [] : inputValue;
+
 		if (
 			value === variableData.selectedValue ||
 			(Array.isArray(value) &&