[libcpu] rv64: support for ARCH_REMAP_KERNEL

[polarvid]

拉取/合并请求描述：(PR description)

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为什么提交这份PR (why to submit this PR)

Introduce support for the ARCH_REMAP_KERNEL configuration, which isolates kernel space in high virtual address regions. This feature is necessary to enhance memory protection and management by segregating user and kernel spaces more effectively.

你的解决方案是什么 (what is your solution)

Changes:

• Updated conditional macros to check for ARCH_REMAP_KERNEL instead of ARCH_KERNEL_IN_HIGH_VA in board initialization files to reflect the new configuration option.
• Modified qemu-virt64-riscv Kconfig and SConstruct files to include and utilize ARCH_REMAP_KERNEL.
• Created a new linker script link_smart.lds for smart linking in qemu-virt64-riscv.
• Updated rtconfig.py to use a more flexible execution path setup.
• Enhanced user address space definitions in lwp_arch.h to support the new virtual address mappings.
• Adjusted kernel memory initialization and mapping logic in c906/mmu.c and virt64/mmu.c to account for high virtual address regions.
• Added Kconfig option to enable ARCH_REMAP_KERNEL for RISCV64 architectures.
• Enhanced memory setup functions to support new mapping scheme, including updates to early page table setup and address relocation logic.

请提供验证的bsp和config (provide the config and bsp)

• BSP: milkv duo, qemu riscv64

• .config:

• action:

milkv duo

QEMU rv64 on RT-Smart

QEMU rv64 on RT-Thread

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当前拉取/合并请求的状态 Intent for your PR

必须选择一项 Choose one (Mandatory):

• 本拉取/合并请求是一个草稿版本 This PR is for a code-review and is intended to get feedback
• 本拉取/合并请求是一个成熟版本 This PR is mature, and ready to be integrated into the repo

代码质量 Code Quality：

我在这个拉取/合并请求中已经考虑了 As part of this pull request, I've considered the following:

• 已经仔细查看过代码改动的对比 Already check the difference between PR and old code
• 代码风格正确，包括缩进空格，命名及其他风格 Style guide is adhered to, including spacing, naming and other styles
• 没有垃圾代码，代码尽量精简，不包含#if 0代码，不包含已经被注释了的代码 All redundant code is removed and cleaned up
• 所有变更均有原因及合理的，并且不会影响到其他软件组件代码或BSP All modifications are justified and not affect other components or BSP
• 对难懂代码均提供对应的注释 I've commented appropriately where code is tricky
• 代码是高质量的 Code in this PR is of high quality
• 已经使用formatting 等源码格式化工具确保格式符合RT-Thread代码规范 This PR complies with RT-Thread code specification