trace2: tolerate failed timestamp formatting #29030

Job	Run time
config	10s
fuzz smoke test	1m 9s
win+Meson build	2m 57s
win build	1m 53s
rust-analysis	1m 36s
sparse	2m 14s
osx-gcc (macos-14)	31s
documentation	8m 26s
osx-meson (macos-14)	31s
osx-clang (macos-14)	32s
static-analysis	5m 16s
linux-sha256 (ubuntu:rolling)	2m 9s
linux-asan-ubsan (ubuntu:rolling)	2m 26s
linux-reftable-leaks (ubuntu:rolling)	1m 55s
osx-reftable (macos-14)	21s
linux-musl-meson (alpine:latest)	41s
linux-TEST-vars (ubuntu:20.04)	1m 39s
almalinux-8 (almalinux:8)	1m 31s
linux32 (i386/ubuntu:20.04)	1m 43s
debian-11 (debian:11)	1m 13s
linux-leaks (ubuntu:rolling)	1m 17s
fedora-breaking-changes-meson (fedora:latest)	1m 9s
linux-meson (ubuntu:rolling)	1m 23s
linux-reftable (ubuntu:rolling)	1m 38s
linux-breaking-changes (ubuntu:rolling)	1m 34s
win+VS build	0s
win+VS test	0s
win test	0s
win+Meson test	0s
	45m 54s

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