Inspired by MPASS.
Can be reimplemented to just use VNASSERT. Imo VNASSERT should be augmented to print stringified assertion + file + line + func instead of just "VNASSERT failed". But then VNPASS would almost literally repeat the first line for panicstr, I don't know if that's a problem apart from looking weird.
Sample output:
```
VNASSERT failed
0xfffff800081b51e8: type VNON
usecount 1, writecount 0, refcount 1
flags ()
lock type ufs: EXCL by thread 0xfffff80003ee06e0 (pid 48, mount, tid 100107)
nlink=0, effnlink=0, size=0, extsize 0
generation=f2bc93f3, uid=0, gid=0, flags=0x0
ino 161326, on dev ufsid/5d6afa2a5db9ebf3
panic: condition vp->v_mflag & 8 not met at /usr/src/sys/kern/vfs_subr.c:3080 (vlazy)
```