Revert "Revert "Add automatic default value for char-type field""

This reverts commit ac1cb3eb26525c868fd7dfeba90b6ee85161c9d8.

Original commit message:

Add automatic default value for char-type field

char type fields are auto-initialized with '\0' when not specified.

Ignore-AOSP-First: security fix
Bug: 206718630
Test: aidl_unittests

Reason for re-submit:
Conflicts resolved in the downstream branches.

Merged-In: I0001331785c0f11e6a1ebab7fef10e690392d417
Merged-In: I69d049f38a71a2c052fc8a7b098dc8525c940505
Change-Id: Ib0ce80da13419192ec8aada05445f2fb2ba5d6ea
(cherry picked from commit 6466daabe5cadd58674ea2c96b7f92255834dc42)
5 files changed