Add APMT ACPI table support for guest uncore PMU

[Arvean-microsoft]

Add receive and install support for the ARM Performance Monitoring Table (APMT) in the guest UEFI firmware. This enables guest VMs to discover uncore PMU MMIO ranges when the host provides an APMT via the UEFI config blob.

Changes:

• Add UefiConfigApmt (0x28) enum value and UEFI_CONFIG_APMT struct
• Add ARM_ACPI_APMT_TABLE_SIGNATURE definition
• Add PcdApmtPtr/PcdApmtSize PCDs (tokens 0x6073/0x6074)
• Parse and validate APMT in PEI phase (Config.c)
• Install APMT in DXE phase via AcpiInstallApmtTable()
• Wire PCDs through both AARCH64 and X64 DSC/INF files

The APMT is optional: it is not added to requiredStructures, and the DXE installer gracefully skips when the table is absent. The parsing and installation follow the same pattern as IORT/PPTT/HMAT.

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[Arvean-microsoft]

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