Enable dummy instruction testing, remove no_bitmanip configuration

Created by: silabs-hfegran

• Made dummy instruction generation available for riscv-dv
• Replaced no_bitmanip configuration with dummy_instr
• Increased per-test timeout to two hours (expect that dummy instr. tests may cause some tests that otherwise would not time out to fail)
• Removed dummy_instr cfg from running in regression with directed tests, as these needs modifications to enable dummy instructions.

ci_check OK