perf(config): use 100 Hz for x86 guest timer

Reduce the normal x86 guest timer frequency from 250 Hz to 100 Hz so
timer-exit overhead can be evaluated against scheduler, network, and
lifecycle latency. Leave aarch64, SEV, and TDX configurations unchanged
until their independent platform guardrails are run.

Author: appcypher

config-libkrunfw_x86_64

@@ -409,11 +409,11 @@ CONFIG_X86_INTEL_TSX_MODE_OFF=y
 # CONFIG_X86_INTEL_TSX_MODE_ON is not set
 # CONFIG_X86_INTEL_TSX_MODE_AUTO is not set
 # CONFIG_X86_USER_SHADOW_STACK is not set
-# CONFIG_HZ_100 is not set
-CONFIG_HZ_250=y
+CONFIG_HZ_100=y
+# CONFIG_HZ_250 is not set
 # CONFIG_HZ_300 is not set
 # CONFIG_HZ_1000 is not set
-CONFIG_HZ=250
+CONFIG_HZ=100
 CONFIG_SCHED_HRTICK=y
 CONFIG_ARCH_SUPPORTS_KEXEC=y
 CONFIG_ARCH_SUPPORTS_KEXEC_FILE=y