File system storage client performance optimizations

[vdusek]

When using the file system storage client, Crawlee for Python is significantly slower than Crawlee for JavaScript.

Processing 1000 requests to a local HTTP server (pydantic models are loaded in advance):

• Crawlee TS - memory: ~1.8s
• Crawlee TS - FS: ~3s
• Scrapy - memory*: 1.9s
• Crawlee Py - new memory: ~1.5s
• Crawlee Py - new FS: ~13.6s

Optimize it.

Ideas:

• atomic write - several FS operations per 1 write
• index file for handled/sequence/forefront

[vdusek]

In the end, this was done as part of #1194, closing.