update gofish version to support supermicro oem

[ben-kulp]

Description:
This PR updates the github.com/stmcginnis/gofish dependency from v0.15.0 to v0.20.0 to gain access to recent improvements and expanded hardware support.

What changed:

• Updated go.mod to use gofish v0.20.0
• Fixed breaking API changes:
  • Updated parseChassisFan function signature to use redfish.ThermalFan instead of redfish.Fan (chassis_collector.go:281)
  • Added type conversion for NetworkPortLinkStatus to PortLinkStatus (chassis_collector.go:428)

Why this update is needed:

• Adds support for Supermicro OEM objects (ComputerSystem, Chassis, Manager, AccountService, UpdateService, DumpService)
• Improves Drive and PCIeDevice/PCIeFunction OEM data exposure
• Updates to Redfish 2023.3 schema bundle for better compatibility with modern hardware
• Includes various bug fixes and stability improvements from versions v0.16.0 through v0.20.0

⚠️ Important Compatibility Note:
The gofish v0.20.0 library changed fan threshold and reading values from float32 to int. This means:

• Fan RPM values that were previously reported as decimals (e.g., 2150.5 RPM) will now be truncated to integers (2150 RPM)
• This affects: Reading, LowerThresholdCritical, LowerThresholdFatal, UpperThresholdCritical, UpperThresholdFatal,
  MinReadingRange, MaxReadingRange
• Recommended: Test with your hardware to ensure fan monitoring and alerting thresholds still work as expected
• This change comes from upstream gofish library and aligns with the Redfish specification

Testing:

• Build completes successfully
• All existing tests pass
• No functional changes to the exporter's behavior (aside from int truncation noted above)
• Confirmed this resolves issue we were seeing with json unmarshalling

time=2025-08-11T16:38:06.486Z level=ERROR msg="error getting processor data from system" target=10.0.0.1 collector=SystemCollector System=HGX_Baseboard_0 operation=system.Processors() error="failed to retrieve some items: [{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_2\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"},{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_1\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"},{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_3\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"},{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_4\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"},{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_5\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"},{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_6\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"},{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_7\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"},{\"link\":\"/redfish/v1/Systems/HGX_Baseboard_0/Processors/GPU_SXM_8\",\"error\":\"json: cannot unmarshal object into Go struct field t1.Actions of type string\"}]"