[arm64][hypervisor][tests] Make test sources more explicit.

This cl does not introduce any functional change to hypervisor tests.
Instead, it makes it more explicit about what is going on to make it
a little easier and clearer for anyone writing new tests.

Change-Id: I977dd65d84a54b0ef0d6d599a0daae09c9de96e8

[x86][hypervisor] Mask CR0.NE and handle writes to CR0

Linux writes values to CR0 that are incompatible with VMX on secondary
processor start-up. Here we mask CR0.NE, which is the only bit that we
need to keep set on secondary processors, to cause a VM exit on writes
to CR0 that don't set NE. The downside of this is that we need to
manually handle the CR0 write including entering long mode when the
guest sets CR0.PG and EFER.LME.

Change-Id: I3acc0c01b938de6f52e57f2fd4bc476c7b7ce185

[hypervisor] Replace zx_vcpu_create_args with entry.

The initial CR3 on BSPs is always 0 and APs begin without paging then
discover the CR3 on their own, so including this as an argument is
unnecessary.

(Also clang-fmt'd)

Change-Id: I88567732252538a0eb239ee1ef4167bf0570f4c1

[utest][hypervisor] Manually construct page tables in guest test

Change-Id: I7728ff4714bcb1241f0319e5d53ff040a6a7013f

[x86][hypervisor] Add x86 vcpu_interrupt test.

This also exposed an issue in our EPT page-fault handling, due to EPT
TLB invalidation not being implemented.

Change-Id: I1a1bf1145d6758015f4ea998ba6098ed0d09c8a7

[utest][hypervisor] Restructure tests for ARM64.

Restructure the guest test so that it can be used on ARM64. The assembly
for the test will come in a follow up CL.

Change-Id: I3286d050ec28cf7b2990741eb2e5005819e4c364

[utest][hypervisor] Add test for traps with ports.

Change-Id: I15df901abece7ac6bca821f678ad760da511cf0a