expose CELL status of a symbol in symtable

Feature or enhancement

Proposal:

symtable symbols have the following predicates, but for some reason no is_cell. Is there a reason for this, or should we expose is_cell as well?

'is_annotated', 'is_assigned', 'is_declared_global', 'is_free', 'is_global', 'is_imported', 'is_local', 'is_namespace', 'is_nonlocal', 'is_parameter', 'is_referenced'

The symbol obviously knows whether it's a cell:

>>> st.get_children()[0].get_symbols()[0]._scope_str
<bound method Symbol._scope_str of <symbol 'x': CELL, USE|DEF_LOCAL>>

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-143549

从 issue 中列出的 symtable Symbol 谓词开始，检查该 symbol 如何报告其内部的 CELL scope。该 issue 链接了 PR gh-143549，因此先审查这项工作。完成的标准是，CELL 状态通过 symtable API 以与现有谓词一致的方式公开。