fix: get_edge_ids() error for 2x2 matrices

[schochastics]

The function now throws a warning and indicates how the matrix is interpreted for backward compatibility

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[krlmlr]

I see that only three packages are affected: corpustools, mwcsr and SEMID. One of the results also hints at a misuse from igraph itself. I still think we should break cleanly and perhaps improve the error message.

[krlmlr]

Another alternative: disallow matrices altogether, ask users to convert matrices with c() or to pass data frames if they have data in columns.

[schochastics]

Fine by me, lets find a way in this PR

[krlmlr]

Let's await revdepchecks in #1793.

[krlmlr]

Run revdepchecks on main again, then here.

[maelle]

@krlmlr friendly reminder to run revdeps 😸

[krlmlr]

Let's ask the downstream maintainers to adapt.

[schochastics]

PRs send to the 3 packages. Should we close this PR then?

[krlmlr]

Closing, let downstream break.