docs/projects/fmcomms2: add doc for FIR_filter

I updated the code in TCL console and diagrams: fmcomms2_vivado_ref_tx
and fmcomms2_vivado_interp_fir_tx.
Updating the code according to TODO notes from Iulia:
Clarification some commands and update some links.
Updating steps for debug in iio osciloscope.
Updating images in the documentation with the latest version of iio
osciloscope. (v0.18-main)

Signed-off-by: BCapota <[email protected]>

Author: BCapota