docs(whats-new): changes in 2.3.5

[dimitri-yatsenko]

Adds Changes in 2.3.5 to What's New in 2.3, and one sentence on 2.3.5 to the page's introduction.

The section covers every fix in the v2.3.5 milestone of datajoint-python:

• the three cascade-delete fixes (delete() ignores a dj.Top restriction and deletes every matching row datajoint-python#1589, Cascade delete removes child rows whose nullable foreign key references nothing datajoint-python#1590, part_integrity="cascade" deletes masters that have no matching part rows datajoint-python#1591), with the workaround for earlier releases;
• deletes restricted by another query, or by a condition containing % (delete() fails when the table is restricted by another query datajoint-python#1610, delete() does nothing when its restriction contains a percent sign datajoint-python#1636);
• PostgreSQL enum types dropped with CASCADE (PostgreSQL: dropping a table drops other tables' columns that share an enum type datajoint-python#1630);
• alter() renames that lost values (alter() loses an attribute's values when it renames a core-type attribute datajoint-python#1631);
• restricted populate(reserve_jobs=True) keeping other workers' jobs (Restricted populate with reserve_jobs deletes other workers' reservations and error records datajoint-python#1594);
• jobs completed_time precision (Jobs: completed_time is truncated to the second, so it can precede reserved_time datajoint-python#1600);
• drop() removing the jobs table (drop() leaves the jobs table behind, and a table re-declared under the same name inherits it datajoint-python#1601);
• alter() resolving foreign keys in the declaring module (Table.alter() resolves foreign keys in the caller's namespace, not the table's declaration context datajoint-python#1602);
• MySQL error 1143 (MySQL error 1143 (column-level SELECT denied) is not translated to AccessError datajoint-python#1586);
• Python 3.15.

It stays a draft until v2.3.5 is tagged, so the text can follow any change to the release.