kvm: prefer the base speed for AMD CPUs + a few refactorings

[winterhazel]

Description

This is a breaking change, so additional discussion may be required. It also contains the changes of #14383, so please review and merge the latter previously.

Many CPUs (notably AMD EPYC) do not advertise a frequency in the model name, so those hosts fell back to CPU max MHz, which can include the turbo frequency. Since the host CPU speed is used to compute host capacity (cpus * speed) and the CPU quota of VMs with CPU cap enabled, using a turbo value is not correct because it is not a frequency the CPU can actually sustain.

This PR inserts the CPU frequency sysfs files (/sys/devices/system/cpu/cpu0/cpufreq/base_frequency, then scaling_max_freq) before the lscpu maximum frequency fallback, so the resolution order becomes:

1. base frequency advertised in the lscpu Model name field (x86) or CPU dynamic MHz (s390x)
2. CPU frequency sysfs file (base_frequency, then scaling_max_freq)
3. lscpu CPU max MHz
4. lscpu host capabilities
5. libvirt NodeInfo.mhz

Behaviour for Intel hosts (whose model name carries @ x.xxGHz) is unchanged.

Additionally, I made a few refactorings throughout the KVMHostInfo file.

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)
• Build/CI
• Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Screenshots (if appropriate):

How Has This Been Tested?

Tests are still pending.

[winterhazel]

@blueorangutan package

[blueorangutan]

@winterhazel a [SL] Jenkins job has been kicked to build packages. It will be bundled with no SystemVM templates. I'll keep you posted as I make progress.

[codecov]

Codecov Report

❌ Patch coverage is 89.47368% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 20.22%. Comparing base (0a5bf30) to head (1809b0c).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
...org/apache/cloudstack/utils/linux/KVMHostInfo.java	92.72%	4 Missing ⚠️
...ervisor/kvm/resource/LibvirtComputingResource.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #14384      +/-   ##
============================================
+ Coverage     20.05%   20.22%   +0.17%     
- Complexity    20656    20765     +109     
============================================
  Files          6427     6426       -1     
  Lines        584905   580203    -4702     
  Branches      71658    71036     -622     
============================================
+ Hits         117278   117329      +51     
+ Misses       454802   450165    -4637     
+ Partials      12825    12709     -116     

Flag	Coverage Δ
uitests	3.69% <ø> (-0.04%)	⬇️
unittests	21.51% <89.47%> (+0.19%)	⬆️

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[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✔️ debian ✔️ suse15. SL-JID 19515