progress: use 'encoding.colwidth' to get column width of output line correctly
Before this patch, 'progress' extension applies 'len' on byte sequence
to get column width of it, but it causes incorrect result, when length
of byte sequence and columns in display are different from each other
in multi-byte characters.
This patch uses 'encoding.colwidth' to get column width of output line
correctly, even if it contains multi-byte characters.
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Ran 20 tests in 0.000s
OK