Remove vexide_tdata section or extract it

[lewisfm]

The official Rust linker script won't have our vexide_tdata section, so we'll have to extract it into a separate file or remove it.

[lewisfm]

Here is an implementation of task locals that does not use vexide_tdata and also avoids copying structs that aren't guaranteed to be Copy: 6b5b3d3