v1.4.0

Added

* Added support for custom CPU templates allowing users to adjust vCPU features
  exposed to the guest via CPUID, MSRs and ARM registers.
* Introduced V1N1 static CPU template for ARM to represent Neoverse V1 CPU
  as Neoverse N1.
* Added support for the `virtio-rng` entropy device. The device is optional. A
  single device can be enabled per VM using the `/entropy` endpoint.
* Added a `cpu-template-helper` tool for assisting with creating and managing
  custom CPU templates.

Changed

* Set FDP_EXCPTN_ONLY bit (CPUID.7h.0:EBX[6]) and ZERO_FCS_FDS bit
  (CPUID.7h.0:EBX[13]) in Intel's CPUID normalization process.

Fixed

* Fixed feature flags in T2S CPU template on Intel Ice Lake.
* Fixed CPUID leaf 0xb to be exposed to guests running on AMD host.
* Fixed a performance regression in the jailer logic for closing open file
  descriptors. Related to:
  [#3542](https://github.com/firecracker-microvm/firecracker/issues/3542).
* A race condition that has been identified between the API thread and the VMM
  thread due to a misconfiguration of the `api_event_fd`.
* Fixed CPUID leaf 0x1 to disable perfmon and debug feature on x86 host.
* Fixed passing through cache information from host in CPUID leaf 0x80000006.
* Fixed the T2S CPU template to set the RRSBA bit of the IA32_ARCH_CAPABILITIES
  MSR to 1 in accordance with an Intel microcode update.
* Fixed the T2CL CPU template to pass through the RSBA and RRSBA bits of the
  IA32_ARCH_CAPABILITIES MSR from the host in accordance with an Intel microcode
  update.
* Fixed passing through cache information from host in CPUID leaf 0x80000005.
* Fixed the T2A CPU template to disable SVM (nested virtualization).
* Fixed the T2A CPU template to set EferLmsleUnsupported bit
  (CPUID.80000008h:EBX[20]), which indicates that EFER[LMSLE] is not supported.