This removes a lot of boilerplate `Print` functions in favor of a
CRTP-based approach that uses a `Label` field as an automatic prefix.
This `Label` is also made available for other purposes, particularly
`IdKind` crash messages in this change. In particular, for
`RequireIdKind` in node_stack.h from using numeric IdKinds (e.g., 5 and
24) to something that will print `IdKind(<label>)` (this came up
recently on #toolchain).
While I'm in here, also doing some other tinkering:
- Moving operators to be `friend` members, to reduce the extra
templating now that the base types are templated.
- Adjusts IntId diagnostics from `int [...]` to `int(...)` for
consistency with other id printing.
- Changes InstBlockId's label from "block" to "inst_block", since we
have multiple blocks now.
- Fixes StructTypeFieldsId to use "struct_type_fields" instead of
"type_block" (from `TypeBlockId`)
- Does some more adjustments from camelCase to snake_case for
consistency
Jon Ross-Perkins
bc24a6c5d8