refactor: adapt axvm refactor

[ZR233]

This pull request introduces significant refactoring and modernization to the arm_vcpu crate, focusing on improved modularity, architectural clarity, and compatibility with the axvm_types workspace. The most important changes include a redesign of per-CPU and vCPU abstractions to remove generic parameters, the addition of a new AxVCpuExitReason enum for VM exit handling, a new HAL (Hardware Abstraction Layer) interface for CPU operations, updates to dependencies and metadata, and adjustments to build and CI configurations for the aarch64-unknown-none-softfloat target.

Architectural Refactoring and HAL Abstraction

• Removed generic parameters (AxVCpuHal) from Aarch64PerCpu and Aarch64VCpu, simplifying their usage and initialization. Introduced a new trait CpuHal and related initialization logic in lib.rs for hardware abstraction, along with default NOP implementations and safe singleton initialization. ([[1]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-cfbd13fb57529c6ffb629101fb244d55a2746c59484e7a9978342c34995c3b8eL1-R32), [[2]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-cfbd13fb57529c6ffb629101fb244d55a2746c59484e7a9978342c34995c3b8eL78-R70), [[3]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-c81313374d24e5697ee5c347b11fc7b156830230764577b85c5180a3ef7f1ecdL1-R14), [[4]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-c81313374d24e5697ee5c347b11fc7b156830230764577b85c5180a3ef7f1ecdL40-R52), [[5]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-b1a35a68f14e696205874893c07fd24fdb88882b47c23cc0e0c80a30c7d53759R13-R24), [[6]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-b1a35a68f14e696205874893c07fd24fdb88882b47c23cc0e0c80a30c7d53759R39-R82))
• Refactored IRQ handling to use the new HAL (handle_irq), eliminating the need for per-CPU function pointers or OnceCell. ([[1]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-1b3d9f91d532261d2032e8f484185b3c4bc5377fb42b19e780b751e936dd33e1L284-R285), [[2]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-1b3d9f91d532261d2032e8f484185b3c4bc5377fb42b19e780b751e936dd33e1R9-R19))

VM Exit Reason Standardization

• Added a comprehensive and well-documented AxVCpuExitReason enum to src/exit.rs, capturing all major categories of VM exits (I/O, system events, power management, multiprocessing, errors, etc.) in a forward-compatible, extensible manner. ([src/exit.rsR1-R191](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-df574c6f1903e886ddf07734496e1891b71f4507e4988e334d907b74dcb2b006R1-R191))
• Updated exception and vCPU modules to use the new AxVCpuExitReason and types from axvm_types. ([[1]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-1b3d9f91d532261d2032e8f484185b3c4bc5377fb42b19e780b751e936dd33e1R9-R19), [[2]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-c81313374d24e5697ee5c347b11fc7b156830230764577b85c5180a3ef7f1ecdL1-R14))

Dependency and Metadata Updates

• Migrated from axaddrspace and related crates to axvm_types for address and device types, updating all usages accordingly. ([[1]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-1b3d9f91d532261d2032e8f484185b3c4bc5377fb42b19e780b751e936dd33e1R9-R19), [[2]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-799cbab61f90a6e923db567539632f95c9b72c073f817328c18a6b196220e929L1-R3), [[3]](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-c81313374d24e5697ee5c347b11fc7b156830230764577b85c5180a3ef7f1ecdL1-R14))
• Updated Cargo.toml to add categories and keywords, adjust dependencies (e.g., update aarch64-cpu to 11.0), and reorganize metadata for clarity and workspace compatibility. ([Cargo.tomlL2-L35](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-2e9d962a08321605940b5a657135052fbcef87b5e360662bb527c96d9a615542L2-L35))

Build and CI Improvements

• Added .cargo/config.toml to set the default build target to aarch64-unknown-none-softfloat. ([.cargo/config.tomlR1-R2](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-9a4f3e4537ebb7474452d131b0d969d89a51286f4269aac5ef268e712be17268R1-R2))
• Updated GitHub Actions workflow to use a newer nightly toolchain and to build and deploy documentation for the correct target directory. ([.github/workflows/ci.ymlL47-R59](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-b803fcb7f17ed9235f1e5cb1fcd2f5d3b2838429d4368ae4c57ce4436577f03fL47-R59))

Exception and Debug Logging Enhancements

• Improved synchronous exception logging to include additional register values (FAR_EL2, HPFAR_EL2, SPSR_EL2) for better debugging. ([src/exception.rsR294-R303](https://github.com/arceos-hypervisor/arm_vcpu/pull/46/files#diff-1b3d9f91d532261d2032e8f484185b3c4bc5377fb42b19e780b751e936dd33e1R294-R303))

These changes collectively modernize the codebase, improve maintainability, and prepare the crate for further development and integration in the arceos-hypervisor ecosystem.