trace2: tolerate failed timestamp formatting #29028

Job	Run time
config	7s
fuzz smoke test	1m 2s
static-analysis	6m 23s
win build	1m 40s
rust-analysis	1m 58s
sparse	2m 22s
documentation	7m 9s
win+Meson build	2m 54s
osx-clang (macos-14)	25s
osx-gcc (macos-14)	30s
osx-meson (macos-14)	28s
osx-reftable (macos-14)	31s
fedora-breaking-changes-meson (fedora:latest)	1m 15s
linux-meson (ubuntu:rolling)	1m 32s
linux-reftable-leaks (ubuntu:rolling)	1m 36s
debian-11 (debian:11)	13s
linux-TEST-vars (ubuntu:20.04)	1m 30s
linux-breaking-changes (ubuntu:rolling)	1m 39s
almalinux-8 (almalinux:8)	1m 17s
linux-leaks (ubuntu:rolling)	15s
linux32 (i386/ubuntu:20.04)	1m 32s
linux-asan-ubsan (ubuntu:rolling)	2m 51s
linux-reftable (ubuntu:rolling)	18s
linux-sha256 (ubuntu:rolling)	2m 6s
linux-musl-meson (alpine:latest)	40s
win+VS build	0s
win+VS test	0s
win test	0s
win+Meson test	-1s
	42m 12s

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