Rollup merge of #129124 - aDotInTheVoid:rdj-hashmap-3, r=GuillaumeGomez

rustdoc-json: Use FxHashMap from rustdoc_json_types

Alternative to #110051 and #127456.

This lets us avoid rehashing the json index after building it by using the same hashmap type in construction and in rustdoc_json_types. The above PR's tried to do this by having rustdoc_json_types get the same hashmap that rustdoc has via rustc_data_structures. However, this can be made simpler if we change rustdoc instead.

For the rustdoc-type republish on crates.io, It will filter out the `pub use`, and not change source at all. https://github.com/aDotInTheVoid/rustdoc-types/pull/30. That code [already replaces the hashmap](https://github.com/aDotInTheVoid/rustdoc-types/blob/8d6528669ec64c2af43d1c79a228b7711cefdad7/update.sh#L11) to use the one in `std::collections` (instead of `FxHashMap`)

try-job: dist-arm-linux

r? ``@GuillaumeGomez``