Escape filenames created for Variant type subcolumns

Escape filenames created for Variant type subcolumns in Wide data part of MergeTree tables. This change breaks compatibility with old tables with Variant/Dynamic/JSON data types. It fixes storing types with special symbols inside Variant (like DateTime with specific timezone that contains \). Escaping can be disabled by changing MergeTree setting escape_variant_subcolumn_filenames (to keep compatibility disable this setting in the config for MergeTree or set compatibility setting to the previous version before upgrade). Resolves #69590. #87300 (Pavel Kruglov).