[lldb][Process/FreeBSDKernel] Remove libfbsdvmcore support (#181283)
Due to libfbsdvmcore, adding new features requires modifying both
`ProcessFreeBSDKernelFVC` and `ProcessFreeBSDKernelKVM` which also
requires testing on both. This is highly inefficient while the user base
of fvc is currently invisible since most package manager don't ship
libfbsdvmcore with LLDB.
There is still demand for cross-platform kernel dump debugging. This
will be implemented in future either by cloning and embedding kvm
interface into LLDB or unifying dump formats to ELF core with
minidump-to-elf conversion tool on FreeBSD side.
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Signed-off-by: Minsoo Choo <minsoochoo0122@proton.me>