Since b52808f1ad `cargo` respects the
`$NIX_BUILD_CORES` variable by utilizing `--test-threads`. However, the
`eva` package also parsed the arguments during the test-phase which
caused a failure since `--test-threads` isn't expected by eva's
argparser[1].
Ths fix is in a pending PR[2] that can be applied on top to fix the
build.
[1] https://hydra.nixos.org/build/126069084
[2] https://github.com/NerdyPepper/eva/pull/37
Changes the default fetcher in the Rust Platform to be the newer
`fetchCargoTarball`, and changes every application using the current default to
instead opt out.
This commit does not change any hashes or cause any rebuilds. Once integrated,
we will start deleting the opt-outs and recomputing hashes.
See #79975 for details.
