Remove TxConfig and RxConfig API.

Originally we plan to accelerate the execution time by parallelly
running the config function of DUT and instrument. But it turns
out that simplifying the API to make the development easier is
more important than the speed. Therefore, we combine the functions
to the later one. For example, the command sequence of Tx test is:

- dut.TxConfig
- inst.TxConfig
- dut.TxStart
- inst.TxMeasure
- dut.TxStop
- return inst.TxGetResult

So the logic of dut.TxConfig moves to dut.TxStart, and the logic of
isnt.TxConfig moves to inst.TxMeasure.

BUG=chromium:713589
TEST=make test

Change-Id: I34a28722d9ec5c2db22728204056f7d1bb989a4c
Reviewed-on: https://chromium-review.googlesource.com/483180
Commit-Ready: Chih-Yu Huang <akahuang@chromium.org>
Tested-by: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Joel Kitching <kitching@chromium.org>
8 files changed