Remove duplicated functions: RC encoder

• Related issues: #2425 (closed)
• Requested reviewers:

Reason why this change is needed

• The core-coder duplicates RC encoder functions.

Description of the change

• Removal of duplications of RC encoder functions.
• Removes cca 220 lines of source code.

Affected operating points

• All is BE.

Closes #2425 (closed)