edit: add qsv edit command

[rzmk]

Adds the qsv edit command for qsv and qsvlite, which allows replacing a cell's value specified by a column and row.

qsv edit <filepath> <col> <row> <value>

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Notes:

• Select a column by name, index, or the last column with _
• -n, --no-headers to allow for editing the header row and using it as row index 0
• -o, --output to output to a file
• Shell completions for qsv edit
• 4 tests for qsv edit

Based on #2046.

[rzmk]

I think it'd be useful if there's also an in-place version of this command when given a file (perhaps a flag?).

[jqnatividad]

I think it'd be useful if there's also an in-place version of this command when given a file (perhaps a flag?).

Yep! I agree that'd be useful... merged just the same as we keep iterating...