Unified Logging now outputs a special empty decorator `[ ]` followed by a space after newlines in multiline log messages. This change allows unambiguous parsing of Unified Logging output.

To illustrate the change, consider the output of `log_info(gc)("A\n[gc] B");`:
```
[gc] A
[ ] [gc] B
```
It is possible to parse this multiline message unambiguously. This was previously not possible, as the output was
```
[gc] A
[gc] B
```
which could (and likely would be) parsed as two distinct log messages `A` and `B`.

Tools that currently deal with multiline parsing ambiguities in Unified Logging require an update. The updates will likely result in simpler and more robust implementations.