Revert^2 "Reduce number of allocation when writing string vec"

This reverts commit 761dc35d.

Reason for revert: relanding with fix for implicit conversion

Test: build trusty_test_xts
Flag: EXEMPT bug fix
Bug: 438750707
Change-Id: Ib5e0b97f6748434acf6d42df5c972122e3ff2694