Backport fix for bitmatrix matmul regression 1.11.1 to 1.11.2

[jakobnissen]

Fix #56954.

[jakobnissen]

I added the backport 1.11 label, but I have no strong opinions on whether this is backport-worthy.
Note that it does now call iszero in generic matmul, so it may fail for custom number types where addition and multiplication is defined, but Base.zero isn't.

[giordano]

You're already targeting the 1.11 branch, so there's nothing to backport? Or am I missing something?

[jakobnissen]

I probably just doesn't understand how backporting works. Are you saying it's done automatically from master with the label? I thought the label was just used for communication.
If the label is going to mess things up, feel free to remove it

[giordano]

Are you saying it's done automatically from master with the label?

Yes

[KristofferC]

But in this case the label + master doesn't really work because LinearAlgebra is moved out to its own separate repo on master but not on 1.11.