Add runtime validation for ELPA complex BLOCK2 kernels

[Growl1234]

See #7784 for the background:

A GCC 15.2 code-generation bug has caused ELPA's double-complex AVX/AVX2 BLOCK2 kernels to return incorrect eigenvectors (marekandreas/elpa#77).

The issue is reliably reproducible in an ELPA-only test and affects ABACUS LCAO multi-k calculations using ks_solver = genelpa. The eigenvalues remain correct, but the returned eigenvectors have large residual and orthogonality errors, which can subsequently corrupt the density matrix, SCF convergence, total energy, forces, stress, and other wavefunction-dependent quantities.

This PR adds a runtime safety check for ELPA's complex 2-stage BLOCK2 kernels used by genelpa:

When an AVX, AVX2, or AVX512 BLOCK2 kernel is selected, ABACUS runs a small deterministic eigensolver test once per process and verifies both the eigenpair residual and eigenvector orthogonality. If the linked ELPA library fails the check, ABACUS aborts with an explicit error instead of continuing with returning wrong results. If users encounter this error they can simply switch to another eigensolver, such as elpa, scalapack_gvx, etc.

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