Auto merge of #102586 - Dylan-DPC:rollup-g107h6z, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #100451 (Do not panic when a test function returns Result::Err.)
 - #102098 (Use fetch_update in sync::Weak::upgrade)
 - #102538 (Give `def_span` the same SyntaxContext as `span_with_body`.)
 - #102556 (Make `feature(const_btree_len)` implied by `feature(const_btree_new)`)
 - #102566 (Add a known-bug test for #102498)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors