This adds SemIR structs and implements building `observe` lists, as well
as naming, formatting, and importing `observe` declarations.
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Co-authored-by: Dana Jansens <danakj@orodu.net>
Add import/ and export/ under function/. Move most top-level tests to a
new basics/ with subdirectories for `import` directives and `inline
Cpp`. Add subdirectory for primitive type handling. Move all `reverse/`
tests to somewhere else, typically under an `export/` directory.
I split two test files up: constexpr.carbon got split into var/ and
function/ pieces, and reverse/simple.carbon was inlined into
namespace/export.carbon. The rest are just simple renames.
Özgür T. ÖnsoyandDana Jansens
Richard Smith