Rename assets_fetch.py to fetch_assets.py

[NadeemYaseen]

Motivate of the pull request

• [x ] To address an existing issue. If so, please add GH or Jira ID here:
• Breaking new feature. If so, please describe details in the description part.

Which submodule does this change impact ?

Rename assets_fetch.py to fetch_assets.py

• Backend
• FOEDAG_rs
• IP_Catalog
• Raptor_Tools
• yosys_verific_rs
• zephyr-rapidsi-dev
• Github CI

What does this pull request change?

Verified that the following tests passed locally before PR was created.

• make tests/batch_all
• RunGJC.tcl

Not needed as only renaming a utility script

Impact of the pull request

• Require a change on Quality of Results (QoR)
• Break back-compatibility. If so, please list who may be influenced.