jsonrpc: add fresh message count to the archive-link chatlistitem variant (#3920)

this is a followup to #3918

I went with option "C" from my comment:
https://github.com/deltachat/deltachat-core-rust/pull/3918#issuecomment-1371224339

- Archive link is (still) very different from a normal chat, so most of the options would be empty / not relevant
- avatar path is not needed as desktop renders it differently anyway,
it's not really a chat like saved messages or device messages where it made more sense
for the core to supply the icon, vs. using the svg directly.
- translating the string in the coreas stock-string is more annoying than doing it from the ui, especially when
this special pseudo chat has different rendering anyway so also no need to provide a name property

CHANGELOG.md

@@ -17,6 +17,7 @@
 
 ### API-Changes
 - jsonrpc: add python API for webxdc updates #3872
+- jsonrpc: add fresh message count to ChatListItemFetchResult::ArchiveLink
 - Add ffi functions to retrieve `verified by` information #3786
 
 ### Fixes