stdlib, resources: depricated workload

- Added WrokloadResource in resource.py.

- depricated Workload and CustomWorkload.

- changed iscvmatched-fs.py with obtain resource for workload to test.

Change-Id: I2267c44249b96ca37da3890bf630e0d15c7335ed
Note: change example files back to original

configs/example/gem5_library/riscvmatched-fs.py

@@ -43,6 +43,7 @@ from gem5.utils.requires import requires
 from gem5.isas import ISA
 from gem5.simulate.simulator import Simulator
 from gem5.resources.workload import Workload
+from gem5.resources.resource import obtain_resource
 
 import argparse
 
@@ -76,7 +77,7 @@ board = RISCVMatchedBoard(
 # In the case where the `-i` flag is passed, we add the kernel argument
 # `init=/root/exit.sh`. This means the simulation will exit after the Linux
 # Kernel has booted.
-workload = Workload("riscv-ubuntu-20.04-boot")
+workload = obtain_resource("riscv-ubuntu-20.04-boot")
 kernel_args = board.get_default_kernel_args()
 if args.to_init:
     kernel_args.append("init=/root/exit.sh")