Revert "[vm] Refactor Location to use either dart::Register or dart::host::Register"

This reverts commit 60b3643e8eb5f86f4b15a7791c201d85a5864c58.

Reason for revert: Broke Windows+simulator builds. (Template instantiation checks are different on Windows than on Linux/MacOS)

Original change's description:
> [vm] Refactor Location to use either dart::Register or dart::host::Register
> 
> Refactoring motivation: go/dart-simulated-ffi
> 
> * template Location and PairLocation with <dart::Register, dart::FpuRegister> or <dart::host::Register, dart::host::FpuRegister>
> * move RegisterName and FpuRegisterName from assembler to constants
> 
> Change-Id: I266b97ef1f0493c184f4486c7a0482845d4ac644
> Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-bare-linux-release-simarm-try, vm-kernel-precomp-bare-linux-release-simarm64-try, vm-kernel-precomp-linux-debug-x64-try, vm-kernel-linux-debug-simdbc64-try
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/97312
> Commit-Queue: Daco Harkes <dacoharkes@google.com>
> Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
> Reviewed-by: Samir Jindel <sjindel@google.com>

TBR=vegorov@google.com,sjindel@google.com,dacoharkes@google.com

Change-Id: I8b4721e3ddbe1d32c3b553555064868bce5ea089
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-bare-linux-release-simarm-try, vm-kernel-precomp-bare-linux-release-simarm64-try, vm-kernel-precomp-linux-debug-x64-try, vm-kernel-linux-debug-simdbc64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/98843
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>