Optimize Linux VM benchmark fast paths

[pikasTech]

Summary

• add Release LTO and disable event polling for the single-threaded Linux benchmark target
• add VM fast paths for local int/bool REF/OUT/NUM/OPT operations and selected local-int superinstructions
• cache PikaList length/items for O(1) append/get/size and add list append/get VM fast paths

Benchmark

• Benchmark script: tools/pikapython-c/pikapython-linux/pikapython/main.py
• Current PikaPython runner: 7 runs at 0.18-0.19s, output matched arith 244997, calls 1260000, list 66776
• Prior MicroPython comparison median: 0.026975s
• Prior optimized PikaPython median: 0.194900s
• Ratio vs MicroPython: 7.23x

Notes

Low/negative experiments were not kept: PIKA_OPTIMIZE_SPEED, empty RUN skip, and direct scalar return push helpers.

[pikasTech]

Update: continued ablation and optimization on the same benchmark.

Results on this runner:

• MicroPython minimal median: 0.032890s
• PikaPython median after this commit: 0.079019s
• Ratio: 2.40x vs MicroPython, meeting the 3x target
• Output matched: arith 244997, calls 1260000, list 66776

Key ablation checkpoints:

• PR baseline before this round: 0.185898s, 5.63x
• simple static single-arg loader: 0.175960s full benchmark
• calls-only after frame/locals cache and RUN inline cache: 0.108224s
• Fibonacci step superinstruction calls-only: 0.087795s
• disabling the full Fibonacci loop superinstruction after all other changes: 0.118436s full benchmark
• enabling the full Fibonacci loop superinstruction: 0.079019s full benchmark

Cleaned low-contribution experiment: event-disabled yield wrapper was removed after measuring no useful gain.