fix: support ALIBABA_CLOUD_REGION_ID env var as fallback for region_id

[Copilot]

Config only fell back to AGENTRUN_REGION / FC_REGION for region_id, breaking the ALIBABA_CLOUD_* convention followed by every other credential parameter. Users who set ALIBABA_CLOUD_REGION_ID (standard Alibaba Cloud SDK env var) received cn-hangzhou instead of their configured region.

Changes

• agentrun/utils/config.py — add ALIBABA_CLOUD_REGION_ID to the region_id fallback chain; update docstring to document all supported env vars
  • Lookup order: explicit param → AGENTRUN_REGION → FC_REGION → ALIBABA_CLOUD_REGION_ID → "cn-hangzhou"
• tests/unittests/utils/test_config_extended.py — add tests for ALIBABA_CLOUD_REGION_ID resolution and priority ordering

# Now works without requiring AGENTRUN_REGION
os.environ["ALIBABA_CLOUD_REGION_ID"] = "cn-shanghai"
config = Config()
config.get_region_id()  # "cn-shanghai"

[OhYee]

关闭：暂不扩展更多环境变量。

我们倾向于先收敛而非继续累加 env var fallback 链（当前每个字段已有 2-3 个名字并存）。如未来决定全面对齐 ALIBABA_CLOUD_* 标准，会作为一次系统性改造统一处理（同时覆盖 region_id、account_id 等），而非按字段单独 PR。

感谢贡献 🙏