Add test cases for range extension thunks that do not use linkerscripts. These include tests for:
- OutputSection larger than Thumb2 branch range
- Range extension thunks to PLT
- Mix of ARM and Thumb range extension thunks
- Special case of Thumb condition branch with short range of 1Mb
- Thunks drifting out of range
Testing range extension thunks isn't pleasant as testing some of the cases needs a single large OutputSection. I've also found that llvm-objdump doesn't handle large files very well so I've had to do multiple calls with restricted address ranges. The disassembly of branch targets is not good either.