systemc: Add an elaboration_done method to sc_simcontext.

The TLM headers rely on this non-standard function.

Change-Id: Iaedec35f1f363dcf3e1fcdb58a74eb2cdc05ddc0
Reviewed-on: https://gem5-review.googlesource.com/c/15061
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

systemc: Enable some more sc_simcontext related tests.

Now that we bit the bullet and stubbed out sc_simcontext and related
functions a little bit, we can enable a couple more tests. This change
also adds in some functions the new tests expect sc_simcontext to have.

Change-Id: I00b5cc0c6eb658eb689b9c85ed171f290009768d
Reviewed-on: https://gem5-review.googlesource.com/11356
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Minimally implemented the deprecated sc_simcontext.

This is supposed to be deprecated, but is still used in a small way
by the tests.

Change-Id: I94fc32f9e0f03d50c00ce5421926203859064020
Reviewed-on: https://gem5-review.googlesource.com/11352
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>