Disable CPU C-States other than C1 (#16703)

Why I did it
Networking devices need to be responsive. Such responsiveness is harmed when the CPU change state.
There is a latency penalty when a CPU is idle (e.g C2) and need to exit this state to come back to C1 state.
To prevent this from happening the CPU should be forced to remain in C1 state.

How I did it
Generalize the cstate forcing to C1 to all Arista products.
This is done by adding processor.max_cstate=1 to the kernel cmdline for all CPUs.
Additionally Intel CPUs also need intel_idle.max_cstate=0 to fallback to the acpi_idle driver.

How to verify it
Check that processor.max_cstate=1 is present on the cmdline for AMD CPUs
Check that both processor.max_cstate=1 and intel_idle.max_cstate=0 are present on the cmdline for Intel CPUs

files/Aboot/boot0.j2

@@ -615,6 +615,14 @@ write_platform_specific_cmdline() {
         aboot_machine=arista_7280cr3mk_32p4
         flash_size=7382
     fi
+
+    # disable cpu c-state other than C1
+    local cpuvendor="$(sed -nr 's/vendor_id[\t ]*: (.*)/\1/p' /proc/cpuinfo | head -n 1)"
+    cmdline_add processor.max_cstate=1
+    if [ "$cpuvendor" = "GenuineIntel" ]; then
+        cmdline_add intel_idle.max_cstate=0
+    fi
+
     if in_array "$platform" "rook" "magpie" "woodpecker" "sprucefish"; then
         cmdline_add tsc=reliable
         cmdline_add pcie_ports=native
@@ -625,7 +633,6 @@ write_platform_specific_cmdline() {
     if in_array "$platform" "rook" "sprucefish"; then
         cmdline_add iommu=on
         cmdline_add intel_iommu=on
-        cmdline_add intel_idle.max_cstate=0
         read_system_eeprom
     fi
     if in_array "$platform" "rook"; then
@@ -643,7 +650,6 @@ write_platform_specific_cmdline() {
         read_system_eeprom
     fi
     if in_array "$platform" "lorikeet" "hedgehog"; then
-        cmdline_add processor.max_cstate=1
         cmdline_add reassign_prefmem
         read_system_eeprom
     fi