The --extension feature requires that all symbols in extension.o
be available when the libraries are dynamically loaded by dlopen.
Prepending extension.o to the linker command adds the otherwise
omitted symbols to spike's dynamic symbol table.

Disassemble Zicond by default

In general, the strategy has been that the disassembler enables a
maximal set of non-conflicting extensions, thereby doing the right thing
for the largest number of users.

Let debugger control hart availability

This change lets me test OpenOCD's behavior when harts become available.
It only affects how things look to the debugger. Harts that are
"unavailable" still execute code as usual.

Control is implemented through the 2 LSBs of the DMCUSTOM register in
the Debug Module.

sim_t: Add sim_t::add_device()

This is public so libspike users can precisely configure the device bus
without going through the DTS interface

triggers: icount: not to decrease on firing icount trigger with Debug Mode action

The icount decreases on firing beakpoint action but not on entering Debug Mode action.
Reference: https://github.com/riscv/riscv-debug-spec/issues/842

fixup sb_write/sb_read to handle exceptions

Remove duplicate compile options

Use device factories to control dts-construction/dts-parsing/device-instantiation

Plugins should now implement and register a device_factory_t to
configure how that device should be parsed from a FDT, and an optional
default DTS string.

This drops support for command-line flag-based device configuration

This class should implement conditional fdt-based device instantiation,
as well as adding device nodes to the dts

make_dtb is only called here, this simplifies later work
towards refactoring device DTS node generation

These are redundant with sim_t::devices