FlowDrop 2.5.0

Find and Replace, and a regex guard that was switched off on some hosts.

Added: text_replace (flowdrop_node_processor) — the substitution operation the
module lacked. A text, a search, a replace, and a literal-or-regex mode, with a
post-update hook that creates the node type on an existing site.

Fixed: the ReDoS backtrack guard treated a host limit of 0 or a negative number
as a bound, and PCRE reads a negative pcre.backtrack_limit as unlimited — so on
such a host regex_extractor ran with no guard at all. Also fixed: a finished
session kept reporting "Running" until something else wrote to it (#3592435).

One database update. Re-export config if you export config. No @api additions,
no @api removals. See CHANGELOG.md and UPGRADE.md.