[Modules] Make -module-file-info print macro names in deterministic order (#161332)
Developers reported non-deterministic output from `-module-file-info`,
thinking this reflected non-determinism in the .pcm files themselves.
However, it turned out it was the printing that was non-deterministic:
```
$ cat /tmp/a.h
#define FOO 1
#define BAR 2
$ build/bin/clang -cc1 -std=c++20 -x c++ -emit-header-unit /tmp/a.h -o /tmp/a.pcm
$ build/bin/clang -cc1 -module-file-info /tmp/a.pcm | grep -A2 Definitions
Macro Definitions:
FOO
BAR
$ build/bin/clang -cc1 -module-file-info /tmp/a.pcm | grep -A2 Definitions
Macro Definitions:
BAR
FOO
```
Making the output deterministic also simplifies the test.
This is a follow-up to 360c5fe54c0758c73bf85453fd2913f371adc7d5
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