Switch fx_ver_t::as_str from stringstream to append/to_string

[elinor-fung]

Stop using std::stringstream to convert fx_ver_t to a string. It pulls in std::locale (and other things) in all the host binaries when we really just need a simple conversion of the numbers to a string. In some binaries, it was also the only usage of stringstream. In theory, this should also be faster, although this is not a particularly perf-sensitive function (most usage is for when tracing is enabled).

On my local Windows x64 build, the sizes on disk were:

	before (kB)	after (kB)	diff (kB)
apphost	153	136	-17
comhost	189	174	-15
dotnet	172	129	-43
ijwhost	141	101	-40
nethost	131	88	- 43

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Issue Details

---

Stop using std::stringstream to convert fx_ver_t to a string. It pulls in std::locale (and other things) in all the host binaries when we really just need a simple conversion of the numbers to a string. In some binaries, it was also the only usage of stringstream. In theory, this should also be faster, although this is not a particularly perf-sensitive function (most usage is for when tracing is enabled).

On my local Windows x64 build, the sizes on disk were:

	before (kB)	after (kB)	diff (kB)
apphost	153	136	-17
comhost	189	174	-15
dotnet	172	129	-43
ijwhost	141	101	-40
nethost	131	88	- 43

Author:	elinor-fung
Assignees:	-
Labels:	area-Host
Milestone:	-

[vitek-karas]

Nice 👍

[elinor-fung]

/backport to release/8.0

[github-actions]

Started backporting to release/8.0: https://github.com/dotnet/runtime/actions/runs/5894030092