This converts the return value of File::read_link() from String to
ErrorOr<String>.
The rest of the change is to support the potential of an Error being
returned and subsequent release of the value when no Error is returned.
Unfortunately at this stage none of the places affected can utililize
our TRY() macro.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
