[Feature] elastic: structured fuzzy results and message size

[Feature] elastic: structured fuzzy results and message size

- `fuzzy`: replace flat `fuzzy_hashes` with per-match objects from `task:get_fuzzy_results()`
  (rule, symbol, found, queried, type, prob, flag, exact); `fuzzy_nested` toggles nested type
- `size`: `task:get_size()`, requested in #6136

 #6147 added `size` to the document only, but `rspamd_meta` is `dynamic: true`, so without
the mapping the type is inferred per index instead of declared.

Signed-off-by: Dmitriy Alekseev <1865999+dragoangel@users.noreply.github.com>