Use tempdir when testing static files, so temporary directories get dropped automatically

[shekhirin]

Describe the feature

reth/testing/ef-tests/src/cases/blockchain_test.rs

Lines 162 to 165 in 181883c

	// TODO: replace with `tempdir` usage, so the temp directory is removed
	// automatically when the variable goes out of scope
	reth_primitives::fs::remove_dir_all(static_files_dir)
	.expect("Failed to remove static files directory");

Here and in other places where create_test_static_files_dir is used, we need to return both a guard (TempDir) and an actual path to the directory, so the guard gets dropped when goes out of scope and the directory gets deleted.

Additional context

Blocked by #6444

[AbnerZheng]

Can I give it a try?

[shekhirin]

@AbnerZheng hey, I assigned you, but we want to merge #6444 into main first, and then accept new PRs on top of these changes.

[AbnerZheng]

NP, I can take a look first and create the PR after the PR has been merged.

[shekhirin]

hey @AbnerZheng, we just merged the PR into main! So feel free to start working on this 😄