docs: Add ad_dds, util_wfifo, util_var_fifo util_pack IP Cores

[gastmaier]

PR Description

Cherry-picked from the doc-ips branch

b09fecdc0 docs: Add common/ad_dds IP core 4cd49679e docs: Add util_wfifo IP core dd87ffb81 docs: Add util_var_fifo IP core 456b04da0 docs: Add util_extract IP core

These IPs are not owned by anyone.

PR Type

• [ ] Bug fix (change that fixes an issue)
• [ ] New feature (change that adds new functionality)
• [ ] Breaking change (has dependencies in other repos or will cause CI to fail)

PR Checklist

• [ ] I have followed the code style guidelines
• [ ] I have performed a self-review of changes
• [ ] I have compiled all hdl projects and libraries affected by this PR
• [ ] I have tested in hardware affected projects, at least on relevant boards
• [ ] I have commented my code, at least hard-to-understand parts
• [ ] I have signed off all commits from this PR
• [ ] I have updated the documentation (wiki pages, ReadMe files, Copyright etc)
• [ ] I have not introduced new Warnings/Critical Warnings on compilation
• [ ] I have added new hdl testbenches or updated existing ones