mayMatchJson method
Whether an entry whose logEntryJsonText is entryJson can satisfy this condition: the needle is
searched in the lowercased JSON text, without decoding the entry, which costs several times more.
Only drops rows that cannot match: the message and the error text appear verbatim in the JSON,
except for the characters JSON escapes and the : Dart puts between error type and message; a
needle containing any of those is not checked here (true), matches decides after decoding.
Implementation
bool mayMatchJson(String entryJson) => !_isCheckableInJson || entryJson.toLowerCase().contains(needle);