Read lowercase bond orders and aromatic flags from chem_comp_bond

[raashish1601]

Fixes #951.

The file in #951 writes chem_comp_bond in lowercase (doub ... n n). _parse_intra_residue_bonds() already upper-cases value_order, but not pdbx_aromatic_flag, so the lookup key becomes e.g. ("DOUB", "n"), which is not in COMP_BOND_ORDER_TO_TYPE, and every intra-residue bond falls back to BondType.ANY. Both items are case-insensitive in the PDBx/mmCIF dictionary (ucode), so lowercase files are valid.

get_component() has the same lookup without any upper-casing, so a component with lowercase values raises a KeyError there.

This upper-cases both values in both places.

Tests: test_lowercase_bond_order (lowercases both columns of 1l2y.cif and compares the bonds with the original) and test_lowercase_bond_order_in_component (same for TYR.cif and get_component()). Both fail on main and pass with the change. I ran tests/structure/io and tests/structure/test_info.py in a Linux container (2167 passed, 1 skipped), using the CCD from the 1.7.1 wheel since the build there had no internet CCD setup. ruff check and ruff format --check pass.