boards: riscv: add RISCV32 Virtual board made with Renode

The RISCV32 Virtual board is a virtual platform made with
Renode as an alternative to QEMU. Contrary to QEMU, the
peripherals of this platform can be easily configured by
editing the `riscv32_virtual.repl` script and the devicetree
files accordingly, this allows certain hardware configurations
that only exist in proprietary boards/SoCs to be tested in
upstream CI.

Added another entry for this board to the excluded platform in
`kernel.timer.timer` test.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>