Logging prefixed with `thread_id:thread_name` is missing a space

[jyn514]

Originally reported in rust-lang/rust#78931.

2:rustc INFO rustc_interface::passes Pre-codegen
2:rustcTy interner             total           ty lt ct all
2:rustc    Adt               :   1078 81.3%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Array             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Slice             :      1  0.1%,  0.0%   0.0%  0.0%  0.0%
2:rustc    RawPtr            :      2  0.2%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Ref               :      4  0.3%,  0.1%   0.1%  0.0%  0.0%
2:rustc    FnDef             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    FnPtr             :     76  5.7%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Placeholder       :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Generator         :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    GeneratorWitness  :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Dynamic           :      3  0.2%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Closure           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Tuple             :     13  1.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Bound             :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Param             :    146 11.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Infer             :      2  0.2%,  0.1%   0.0%  0.0%  0.0%
2:rustc    Projection        :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Opaque            :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc    Foreign           :      0  0.0%,  0.0%   0.0%  0.0%  0.0%
2:rustc                  total   1326         0.2%   0.1%  0.0%  0.0%
2:rustcInternalSubsts interner: #437
2:rustcRegion interner: #355
2:rustcStability interner: #1
2:rustcConst Stability interner: #0
2:rustcAllocation interner: #0
2:rustcLayout interner: #0

I think the issue is that this is multi-line logging, and tracing-tree assumes that there will only be one line?

[davidbarsky]

...and tracing-tree assumes that there will only be one line?

That's correct, yeah. I think that resolving this would take a lot of effort.