fix(core): preserve whitespace in paths

[georgeorange-crypto]

Summary

• stop trimming leading and trailing whitespace in operation paths
• keep existing normalization for leading slashes and repeated slashes
• add a behavior test that writes and reads a file whose name ends with a space

Closes #6577.

Validation

• cargo fmt --check
• cargo test -q -p opendal-core raw::path::tests::test_normalize_path
• OPENDAL_TEST=fs cargo test -q -p opendal --features services-fs,tests --test behavior -- test_read_with_trailing_space
• cargo check -q