Limit wifi item edit content's max length to 500

Bug: 293199910
Test: manual - on "Add network"

(cherry picked from commit 855053c)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:092668676af741719d50ac0f121a8f8461aa21ad)
Merged-In: I303b8c6e0f3c3a1174a047ba98f302042e5db9ae
Change-Id: I303b8c6e0f3c3a1174a047ba98f302042e5db9ae

res/values/styles.xml

@@ -148,6 +148,7 @@
         <item name="android:textAppearance">@android:style/TextAppearance.DeviceDefault.Medium</item>
         <item name="android:textColorHint">?android:attr/textColorSecondary</item>
         <item name="android:minHeight">@dimen/min_tap_target_size</item>
+        <item name="android:maxLength">500</item>
     </style>
 
     <style name="wifi_section">