When computing i18n messages for templates there are two passes.
This is because messages must be computed before any whitespace
is removed. Then on a second pass, the messages must be recreated
but reusing the message ids from the first pass.
Previously ICUs were losing their legacy ids that had been computed
via the first pass. This commit fixes that by keeping track of the
message from the first pass (`previousMessage`) for ICU placeholder
nodes.
// FW-1637
PR Close#33318
5d86e4a9b1