This PR propagates the `AttributeKind` to `SimpleScopedEnvExtension.add`
in attributes created with `register_label_attr`.
This also fixes a nearby stale docstring which referenced `Std`.
---
Closes#3697
[Before](https://github.com/leanprover/lean4/files/14772220/oi.pdf) and
[after](https://github.com/leanprover/lean4/files/14772226/oi2.pdf).
This gets `ByteArray`, `String.Extra`, `ToString.Macro` and `RCases` out
of the imports of `omega`. I'd hoped to get `Array.Subarray` too, but
it's tangled up in the list literal syntax. Further progress could come
from make `split` use available `Decidable` instances, so we could pull
out `Classical` (and possibly some of `PropLemmas`).
#3408 was somewhat large and didn't properly test the symm and label
attribute code after edits to the builtin versions.
This migrates the code for generating labeled attributes from Init back
to Lean so that the required definitions are in scope.
This also addresses a mistake in the symm elaborator that prevented symm
without location information from elaborating.
Both fixes have been tested on the Std test suite and successfully
passed.
