Cleanups: Formatting and comments

[StephanTLavavej]

• Avoid // strengthened putting { on the next line. This is one of the few scenarios where we prefer to use C-style comments.
• Remove double newlines in product code, both within functions (where they were especially distracting) and outside of functions.
  • This would be a low-value cleanup to apply to test code, which I am intentionally not doing.
  • In theory, double newlines can be used to create breaks between distinct groups of code. In practice, we've used them increasingly rarely and inconsistently, so they're more of a distraction than anything useful.
  • I am leaving a few double newlines that are separating license banners.
• Thanks @JMazurkiewicz for noticing that I was modifying generated code! 😻 I've updated grapheme_break_property_data_gen.py accordingly (and verified that the output is identical after clang-formatting).
  • There's a newline embedded at the beginning of our multi-line "TEMPLATE" raw string literals. I took @JMazurkiewicz's suggestion of calling PROP_VALUE_ENUM_TEMPLATE.lstrip() which is sufficient. But then I noticed that DATA_ARRAY_TEMPLATE was the only multi-line string template that we weren't stripping leading whitespace from, which seemed confusing. I think it's better to consistently strip them (so we can pretend that they didn't begin with leading whitespace at all), and then explicitly add a newline to separate the enumerator values from the table.
• Change comments to refer to _Count instead of _Count_raw.
  • Mentioning _Count is overwhelmingly more common; _Uninitialized_value_construct_n_unchecked1 in <xmemory> doesn't even take _Count_raw.
• Fix a comment typo: "Ad hoc" is two words.

[strega-nil-ms]

I've noticed two areas where we may want further changes:

• stl/inc/iterator:255: it doesn't result in the newline going away, but we could change the // strengthened to a /* strengthened */ before a { (I believe it's the only one left
• there are still two newlines in a row between macros in <atomic>

[StephanTLavavej]

Thanks @strega-nil-ms! 😻 I've pushed a conflict-free merge with main, followed by commits for the 2 issues you mentioned. I had originally skipped that <iterator> line because it was too long, but you're right that it's simpler to just change it and get rid of the special case. And great catch for <atomic> - I think I had excluded it because #3406 was in flight, but then I forgot about it.

[StephanTLavavej]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.