This is a style change. Visual Studio defaults to indenting namespace
contents, and this was adopted for a long time, but with the new Vulkan
implementation this was abandoned. However the legacy code borrowed from
the OpenGL ES implementation still used indentation so it was
inconsistent.

The justification for not indenting namespace contents is that
namespaces are merely a way to avoid name clashes with other projects
we don't control directly (and in rare cases internal subprojects when
we want to reuse the same names). Hence the vast majority of files have
a single namespace, and unlike indentation used for ease of discerning
control flow blocks, class contents, or function contents, which can
become highly nested, there is no such readability advantage to
indenting namespace contents.

This is also the Google style recommendation (though no justification or
discussion is provided):
https://google.github.io/styleguide/cppguide.html#Namespace_Formatting

One reasonable counter-argument is consistency with other blocks of
curly brackets, but considering that most namespaces span almost the
entire file, it's a substantial waste of line length.

Because there is no indentation, there's also no need to have the open
and closing brackets line up as a visual aid, like we prefer for other
uses of curly brackets. So we place the open bracket on the same line as
the namespace keyword.

A comment is added to the closing bracket to discern it from other
closing brackets. It also makes it easier to find the end of anonymous
namespaces which typically go at the top of the source file.

This change is make separately from applying clang-format because diff
tools mark all these unindented lines as changes and this makes it hard
to review the smaller style changes made by clang-format. The OpenGL ES
and Direct3D code is left untouched because it is in maintenance mode
and in case of regressions we want easy 'blame' tool usage.

Bug: b/144825072
Change-Id: Ie2925ebd697e1ffa7c4cbdc9a946531f11f4d934
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39348
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>