fix: 🐛 adjust chunk cache key for edge case

[stormslowly]

.

[sorrycc]

补个 e2e 用例？

[stormslowly]

文件数太少了，触发了 cached 宏内部锁机制失效。相同 cache key，各自都调用了 inner ，所以复现不了问题。

pub(crate) fn render_css_chunk(chunk_pot: &ChunkPot, context: &Arc<Context>) -> Result<ChunkFile> {
    use cached::Cached;
    let key = { chunk_pot.stylesheet.as_ref().unwrap().raw_hash };
    {
        let mut cache = RENDER_CSS_CHUNK.lock().unwrap();
        if let Some(result) = cache.cache_get(&key) { return Ok(result.clone()); }
    } 

    fn inner(chunk_pot: &ChunkPot, context: &Arc<Context>) -> Result<ChunkFile> {}
    
    let result = inner(chunk_pot, context);
    let mut cache = RENDER_CSS_CHUNK.lock().unwrap();
    if let Ok(result) = &result { cache.cache_set(key, result.clone()); }
    result
}

[stormslowly]

用例也发现不了，暂时不加了；
还是 build 阶段去缓存 RIO 更高一些