[202205][generate_dump] Revert "Revert generate_dump optimization PR's #2581", add fixes for empty /dump forder and symbolic links

[vadymhlushko-mlnx]

What I did

1. Revert [202205] Revert the show-techsupport optimization PR's #2581
2. Add a fix for the empty /dump folder inside the final tar archive generated by the show techsupport CLI command.
3. Add a fix to not follow the symbolic links to avoid duplicate files inside the final tar archive generated by the show techsupport CLI command.

How I did it

Modify the scripts/generate_dump script.

How to verify it

1. Manual verification

• do the show techsupport CLI command and save output original.tar.gz (with original generate_dump script)
• do the show techsupport CLI command and save output fixes.tar.gz (with the generate_dump script modified by this PR)
• unpack both archives original.tar.gz and fixes.tar.gz
• compare both directories with ncdu & diff --brief --recursive original fixes Linux utilities

2. Run the community tests

• sonic-mgmt/tests/show_techsupport

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)

[liat-grozovik]

@yxieca please refer to this backport as an important enhancement to 202205