(entry_index_specification): accept aspect_specification
In accordance with Ada 2022 RM 9.5.2(8/5); this was not allowed in Ada
2012, but was changed in AI12-0398-1/03.
add dummy test.
(entry_body): directly parse entry_body_formal_part
In Ada grammar the entry_body_formal_part both the
entry_index_specification and the parameter_profile are optional
(because they describe both simple entries and entry families,
both with and without parameters). However, tree-sitter does not
allow rules that match empty strings.
The simplest solution is to directly encode entry_body_formal_part
within the entry_body.
add test.
