Add plaintext WifiConfig SSID length check

Plaintext WifiConfiguration SSIDs need a length check or else an
arbitrary length may be set. Set the max length to 32 characters, as
the minimum length for any SSID encoding is 1-byte per character.

Bug: 343714914
Test: atest WifiConfigurationUtilTest
Change-In: I88994f6c022f7b427aceab3fac6cc876a0ecb4c9
(cherry picked from commit 4a7564305147e97cbd6f8df706c78bf2714eb200)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:3b2ff7586f6961e5f6394b821f926a34942f0f94)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:96f6cc1a875a255c7587946cb6563220ff0b3e19)
Merged-In: I88994f6c022f7b427aceab3fac6cc876a0ecb4c9
Change-Id: I88994f6c022f7b427aceab3fac6cc876a0ecb4c9