feat: Move the SLA filter dropdown to UI folder (#9502)

# Pull Request Template

## Description

I moved the newly created SLA filter dropdown to the UI folder to use in
adding the Linear issue modal.

app/javascript/dashboard/components/ui/Dropdown/DropdownButton.vue

@@ -0,0 +1,47 @@
+<script setup>
+defineProps({
+  buttonText: {
+    type: String,
+    default: '',
+  },
+  rightIcon: {
+    type: String,
+    default: '',
+  },
+  leftIcon: {
+    type: String,
+    default: '',
+  },
+});
+</script>
+<template>
+  <button
+    class="inline-flex relative items-center p-1.5 w-fit h-8 gap-1.5 rounded-lg hover:bg-slate-50 dark:hover:bg-slate-800 active:bg-slate-75 dark:active:bg-slate-800"
+    @click="$emit('click')"
+  >
+    <slot name="leftIcon">
+      <fluent-icon
+        v-if="leftIcon"
+        :icon="leftIcon"
+        size="18"
+        class="flex-shrink-0 text-slate-900 dark:text-slate-50"
+      />
+    </slot>
+    <span
+      v-if="buttonText"
+      class="text-sm font-medium truncate text-slate-900 dark:text-slate-50"
+    >
+      {{ buttonText }}
+    </span>
+    <slot name="rightIcon">
+      <fluent-icon
+        v-if="rightIcon"
+        :icon="rightIcon"
+        size="18"
+        class="flex-shrink-0 text-slate-900 dark:text-slate-50"
+      />
+    </slot>
+
+    <slot name="dropdown" />
+  </button>
+</template>