Remove modification for missing-field-initializers from sources.

Since C++11, we have concrete semantics.
Thus, we rely on it.

Note that, we still need to keep LAZY_INSTANCE_INITIALIZER
because it is a macro used in other project, which may
have missing-field-initializers warning enabled.

Bug: 73270448
Test: Built locally. Treehugger.
Change-Id: Ieb59b25c2936d27c3501d21098b248fac2778f0a
7 files changed