Rollup merge of #86659 - notriddle:notriddle/generics-rustdoc, r=GuillaumeGomez

fix(rustdoc): generics search

This commit adds a test case for generics, re-adds generics data
to the search index, and tweaks function indexing to use less space in JSON.

This partially reverts commit 14ca89446c076bcf484d3d05bd991a4b7985a409.