Fix test manifest options and handle @json type gracefully

[mielvds]

This PR fixes the last outstanding tests for flatten() and frame().
In includes two fixes:

• Options from the test manifest now override the options configured in create_test_options(), instead of the other way around. In case of extractAllScripts, the default is True, while most tests except one expect False. However, in the test manifest False is the default and therefore not explicitly provided. Hence, there was no way to provide this value through the test setup.
• When @type is @json in a frame, it no longer raises an "Invalid JSON-LD syntax" error.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
lib/pyld
canon.py	218	4	98%	27, 180, 565–566
context_resolver.py	102	8	92%	70, 129, 143, 189, 195–197, 221
iri_resolver.py	141	3	98%	307–308, 318
jsonld.py	2440	173	93%	274–278, 359, 396, 401, 411, 428–443, 479–480, 522, 530, 550, 558–559, 667–672, 752–753, 768–769, 829–834, 859–860, 875–876, 886–887, 912–913, 954, 964, 970–974, 985–986, 1019, 1028, 1035, 1100, 1123, 1145–1147, 1157–1160, 1175, 1198, 1210–1213, 1305, 1317–1320, 1340, 1369, 1402, 1406, 1443, 1486, 1504–1507, 1516, 1561, 1664–1671, 1698–1700, 1705, 1726–1729, 1905, 1943, 2376, 2385–2392, 2484, 2511, 2534, 2543, 3059, 3112, 3115, 3178, 3263, 3297, 3305, 3583, 3588, 3590, 3639, 3777–3781, 3847, 3884, 3947, 4167–4168, 4182, 4470, 4604, 4638, 4667–4670, 4696–4697, 4880, 4944, 4971, 5045, 5047, 5065, 5163, 5212, 5444, 5446, 5485, 5487, 5496, 5635, 5763, 5850, 5970–5984, 6043–6049, 6116, 6329, 6335–6339, 6378, 6381, 6471–6472, 6481
lib/pyld/documentloader
aiohttp.py	65	22	66%	28–38, 69, 75, 87, 99–107, 118–121, 138, 153–155
requests.py	41	5	88%	55, 69, 81–89
TOTAL	3193	215	93%

Tests	Skipped	Failures	Errors	Time
1673	52 💤	0 ❌	0 🔥	11.087s ⏱️