fix: start extract resource timing before first item

[fengjikui]

Fixes #3518.

Summary

• initialize static extract resource counters when their source pipe starts, before the first item is pulled
• keep dynamic table-name resources on the existing item-driven timing path because their table name is not known before data arrives
• add a regression test that simulates a resource waiting before yielding its first item and verifies the logged resource time includes that wait

Validation

• uv run black dlt/extract/pipe_iterator.py dlt/extract/extract.py tests/extract/test_extract.py
• git diff --check
• uv run pytest tests/common/runtime/test_collector.py tests/extract/test_extract_pipe.py tests/extract/test_extract.py::test_resource_log_time_includes_wait_before_first_item -q
• uv run pytest tests/extract/test_extract.py -q