Add dumping for NamedConstraintId and shorten untagged id printing (#6319)

Adds support to the `dump` debugger command for named constraint ids,
which are printed as `constraint<number>`. While doing so, we print
whether the `constraint` is complete or not, and add the same to
`interface` to match.

And we noticed that the printing of name and name scope ids, which are
not tagged, are very verbose by adding 7 `0`s to them for no reason. So
make the dump output easier to read by dropping 0 prefixes.

Before:
```
name_scope00000000: {inst: inst0000000E, parent_scope: name_scope<none>, has_error: false, extended_scopes: [], names: {name00000000: inst6000000F, name00000001: inst60000011}} {kind: Namespace, arg0: name_scope00000000, arg1: inst<none>, type: type(inst(NamespaceType))} `package`
```

After:
```
name_scope0: {inst: instE, parent_scope: name_scope<none>, has_error: false, extended_scopes: [], names: {name0: inst6000000F, name1: inst60000011}} {kind: Namespace, arg0: name_scope0, arg1: inst<none>, type: type(inst(NamespaceType))} `package`
```

scripts/lldbinit.py

@@ -78,6 +78,7 @@ Example usage:
     id_types = {
         "class": "SemIR::MakeClassId",
         "constant": "SemIR::MakeConstantId",
+        "constraint": "SemIR::MakeNamedConstraintId",
         "symbolic_constant": "SemIR::MakeSymbolicConstantId",
         "entity_name": "SemIR::MakeEntityNameId",
         "facet_type": "SemIR::MakeFacetTypeId",