Remove duplicated code: FD BWE

• Related issues: #2409 (closed)
• Requested reviewers:

Reason why this change is needed

• Harmonization of duplicated FD BWE core-coder functions.

Description of the change

• Harmonization of duplicated FD BWE core-coder functions.
• Removes cca 1,100 lines of source code.

Affected operating points

• All is BE.