Rollup merge of #139795 - jethrogb:jb/sgx-linkage-comments, r=joboet

Clarify why SGX code specifies linkage/symbol names for certain statics

Specifying linkage/symbol name is solely to ensure a single instance between the `std` crate and its unit tests.

Also update the symbol names as items have moved around a bit. The actual name isn't that important, it just needs to be unique. But for debugging it can be useful for it to point to the right place.

Author: ChrisDenton