feat: display process tree with command line arguments

[behouba]

This PR introduces a new flag --ps-tree-cmd to provide an alternative view of process tree.
Using --ps-tree-cmd it is now possible to display the full command line arguments in the process tree.

Example:

$ checkpointctl inspect /path/to/checkpoint.tar.gz --ps-tree-cmd
counter
└── [1]  bash
    ├── [7]  bash -c 'python counter.py'
    ├── [8]  python counter.py --input data.txt --output result.txt
    ├── [11]  bash -c 'tee output.log'
    └── [20]  tee output.log

[github-actions[bot]]

Test Results

40 tests  +2   40 :heavy_check_mark: +2   1s :stopwatch: ±0s   1 suites ±0     0 :zzz: ±0    1 files   ±0     0 :x: ±0 

Results for commit 9b887b14. ± Comparison against base commit b88a99f5.

:recycle: This comment has been updated with latest results.

[codecov-commenter]

Codecov Report

Patch coverage: 84.44% and project coverage change: +0.14 :tada:

Comparison is base (5d84ffa) 82.43% compared to head (9b887b1) 82.58%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #89 +/- ## ========================================== + Coverage 82.43% 82.58% +0.14% ========================================== Files 4 4 Lines 558 603 +45 ========================================== + Hits 460 498 +38 - Misses 72 77 +5 - Partials 26 28 +2 ``` | [Impacted Files](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/89?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [container.go](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/89?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y29udGFpbmVyLmdv) | `76.01% <72.72%> (-0.18%)` | :arrow_down: | | [tree.go](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/89?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-dHJlZS5nbw==) | `85.82% <76.47%> (-1.36%)` | :arrow_down: | | [checkpointctl.go](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/89?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y2hlY2twb2ludGN0bC5nbw==) | `92.85% <100.00%> (+0.67%)` | :arrow_up: |

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