Add FFmpeg to docker images and fix rocDecode on SLES

[zichguan-amd]

Motivation

Add FFmpeg dependency in docker images and fix SLES rocDecode build failure

Technical Details

Ubuntu image already has ffmpeg installed, adding package install explicitly for readability.
Build FFmpeg 4.4.6 from source in SLES

Fix experimental filesystem not having member functions is_directory() and is_regular_file(), change it to fs::is_directory(entry.path())) and fs::is_regular_file(entry.path())).

Test Plan

Locally tested new SLES docker image

Test Result

All tests pass on gfx1100

Added/Updated documentation?

• Yes
• No, does not apply to this PR.

Included Visual Studio files?

• Yes
• No, does not apply to this PR.

Submission Checklist

• New examples contain proper CMake and Make files.
• I have updated relevant CI workflows and the new examples are being built and tested in CI.
• Check and guard against unsupported ASICs if relevant dependent libraries have limited support.
• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[zichguan-amd]

FFmpeg support is not ready on TheRock, in-kernel mesa driver doesn't support it anymore. Removing the rocDecode FFmpeg tests in another PR