[fbl] Migrate to std::make_unique and remove fbl::make_unique

fbl::make_unique was functionally identical to std::make_unique. There
should be no behavior change in this CL.

The bulk of this CL was prepared via the following zsh script:

    for f in $(git grep -l 'fbl::make_unique<') ; \
    sed -i 's/fbl::make_unique</std::make_unique</' $f

Bug: ZX-3357 #comment remove make_unique
Bug: ZX-3837 #comment remove make_unique
Change-Id: Ic8bf489e4dbf7cb7d2d71ad95aa26018bf776e56