applet.jtag.mec16xx: implement "functional" firmware read and write.

applet.jtag.arc: use Run-Test/Idle to initiate transactions.

applet.jtag: use minimal path through TAP state machine. It is important for some cores (e.g. ARC) to not unnecessarily enter Run-Test/Idle, as this can initiate actions (e.g. R/W transaction.)

applet.jtag: split logging into JTAG-L[owlevel] and JTAG-H[ighlevel].

cli: add --filter-log, for raising the log level of a single component.

applet.jtag.arc: display failed transaction status.

firmware: update libfx2.

applet.jtag.mec16xx: add emergency-erase command.

applet.jtag: enter Run-Test/Idle in JTAGInterface.run_test_idle.

arch.arc.mec16xx: add Flash IP registers. Unfortunately I couldn't get these to do anything...