fix: Docker pull hanging on Windows

[rboni-dk]

IO buffers are smaller on Windows and python's implementation of Popen.communicate() does different things on Windows too (uses thread). Not using communicate is the most likely cause for the process to hang on that OS, so this PR is refactoring how we read from the command output streams to use communicate.

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
dk-installer.py	1238	292	76%	105, 117–129, 162–163, 212, 252–259, 295–296, 338, 388–391, 410–411, 413, 463–492, 496–529, 560–569, 625, 761, 788–793, 865–866, 876, 892–896, 899, 902, 905, 916–949, 1052–1065, 1116–1120, 1131, 1160–1192, 1221, 1263–1264, 1270–1281, 1286, 1359–1361, 1398–1401, 1404–1447, 1456–1464, 1505–1506, 1520, 1547–1549, 1561–1563, 1597–1600, 1686–1689, 1714, 1739–1741, 1777, 1796, 1813–1814, 1821, 1823, 1825, 1932–1934, 1951, 1971–1972, 2015–2016, 2044, 2108–2147, 2188–2195, 2269–2280, 2287–2295, 2365–2390, 2397–2405, 2414–2468, 2472–2497, 2501–2519
TOTAL	1238	292	76%

Tests	Skipped	Failures	Errors	Time
93	0 💤	0 ❌	0 🔥	1.178s ⏱️