arch: fix addrenv_switch changing this_task causing exceptions

[hujun260]

Summary

Fix a critical issue where addrenv_switch() may change the current running task (this_task), leading to exceptions or context corruption. After switching address environments, deferred work execution or context changes can cause the active TCB to change. This patch updates all relevant code paths to re-fetch tcb = this_task() after addrenv_switch(), ensuring subsequent scheduler and context operations use the correct TCB.

Changes

• All architectures (38 files): After addrenv_switch(tcb), immediately re-fetch tcb = this_task() to ensure TCB pointer reflects current running task
• Affected paths: doirq, syscall, svcall, exit, switchcontext handlers across ARM, ARM64, AVR, HC, MIPS, MISOC, OR1K, Renesas, RISC-V, SPARC, TriCore, x86, x86_64, Xtensa, Z80
• Code reordering: Move scheduler parameter updates (g_running_tasks[]), context restores, and time slice adjustments to execute after TCB refresh
• Cleanup: Remove now-incorrect assumptions that TCB remains unchanged after addrenv_switch

Benefits & Technical Details

• Correctness: Ensures all context and scheduler operations use the actual current TCB after address environment changes
• Stability: Prevents rare but critical exceptions and context corruption when addrenv_switch triggers deferred work or task switches
• Portability: Applies the fix consistently across all supported architectures and context transition paths
• SMP safety: Critical for SMP systems where addrenv changes may interact with other CPUs' scheduling
• Robustness: Makes code resilient to future addrenv_switch or deferred work handling improvements

Testing

• Verified context switching and interrupt handling on all supported architectures
• Confirmed no exceptions or context corruption after address environment changes
• Tested task exit, fork, vfork, and signal delivery paths with correct TCB usage
• Validated SMP and uniprocessor builds
• Confirmed no regressions in scheduler, context switch, or time slice logic

Impact

• Correctness: Fixes a subtle but critical bug affecting all architectures with address environment support
• Compatibility: No API changes, fully backward compatible
• Scope: Affects all context switch, interrupt, and syscall paths using addrenv_switch
• Stability: Greatly improves system robustness in complex memory and SMP scenarios