[lldb] [Process/FreeBSDRemote] Introduce arm (32-bit) support

Introduce a NativeRegisterContextFreeBSD for 32-bit ARM platform.
This includes support for GPR + VFP registers as exposed by FreeBSD's
ptrace(2) API.  Hardware breakpoints or watchpoints are not supported
due to missing kernel support.  The code is roughly based on the arm64
context.

It also includes an override for GetSoftwareBreakpointTrapOpcode() based
on the matching code in the PlatformFreeBSD plugin.

Differential Revision: https://reviews.llvm.org/D95696