Rollup merge of #142680 - beetrees:sparc64-float-struct-abi, r=tgross35

Fix passing/returning structs with the 64-bit SPARC ABI

Fixes the 64-bit SPARC part of rust-lang/rust#115609 by replacing the current implementation with a new implementation modelled on the RISC-V calling convention code ([SPARC ABI reference](https://sparc.org/wp-content/uploads/2014/01/SCD.2.4.1.pdf.gz)).

Pinging `sparcv9-sun-solaris` target maintainers: @psumbera @kulikjak
Fixes rust-lang/rust#115336
Fixes rust-lang/rust#115399
Fixes rust-lang/rust#122620
Fixes rust-lang/rust#147883
r? @workingjubilee

Author: jhpratt