[Minor] Migrate lualib/lua_selectors/common.lua to lua_shape

[Minor] Migrate lualib/lua_selectors/common.lua to lua_shape

Replace tableshape with lua_shape in selectors common utilities.

Changes:
- ts.one_of { ... } → T.enum({ ... })
- :is_optional() → :optional()
- Added documentation to schema fields

Schema: digest_schema returns array with optional encoding format
and optional hash algorithm for selector digest operations.