I'm using osqp-eigen v0.7.0, wondering if Hessian Matrix is supporting only symmetric matrix, rather than upper triangular matrix.

My partial code as follows:
```
// symmetric matrix
for (int i = 0; i < n - 1; ++i)
{
hessian.insert(i, i + 1) = 1.0;
hessian.insert(i + 1, i) = 1.0;
}
// upper triangular matrix
for (int i = 0; i < n - 1; ++i)
{
hessian.insert(i, i + 1) = 2.0;
}
```
When I used the symmetric matrix, I got the true solution(I guess). Instead, solver return
```status: problem non convex```
while using upper triangular matrix.

Reproduce the reported behavior using the symmetric and upper-triangular Hessian snippets with osqp-eigen v0.7.0, then trace how the Hessian is passed to the solver. Compare the resulting status with the expected matrix representation and document or test the supported behavior so the distinction is unambiguous.

Written by the indexing model from the issue text.