[Infrastructure] Add O2 linter

[vkucera]

Adds a GitHub action that runs a script that checks for O2-specific issues in the code.
The script can run standalone, taking paths of files as arguments.
When running in the GitHub action on the pull_request event, the script tests files modified by the PR and generates error messages as GitHub annotations which appear as comments on the relevant lines or at the top of the file in case of per-file tests.
When running in the GitHub action on the push event, the script tests files modified in the branch w.r.t. the main branch and does not produce annotations.
False positives should be rare but, if any, they can be silenced per line for most of the tests by adding a comment in a given format.

Implements the following tests.

Bad practice:

• included iostream
• importing names from the std namespace
• using directives in headers
• missing std:: prefix for common names from the std namespace
• unnecessary use of ROOT entities
• use of external pi
• adding/subtracting of 2 pi
• multiples/fractions of pi for existing equivalent constants
• use of TDatabasePDG
• use of hard-coded PDG codes
• unnecessary call of Mass() for a known PDG code
• non-O2 logging
• not using const refs in range-based for loops
• not using const refs in process function subscriptions
• usage of workflow options in defineDataProcessing

Documentation:

• mandatory documentation of C++ files

Naming conventions:

• functions
• variables
• macros
• constexpr constants
• namespaces
• defined types
• enumerators
• classes
• structs
• O2 columns
• O2 tables
• O2 workflows
• explicit task names
• workflow files
• configurables
• C++ files
• Python files

PWG-HF specific conventions:

• PWGHF: names of structs and classes
• PWGHF: names of task files
• PWGHF: order of struct members

[github-actions]

This PR has not been updated in the last 30 days. Is it still needed? Unless further action is taken, it will be closed in 5 days.

[github-actions]

This PR has not been updated in the last 30 days. Is it still needed? Unless further action is taken, it will be closed in 5 days.

[ktf]

I like this, why is it still draft?

[vkucera]

I like this, why is it still draft?

Pending discussion with @ddobrigk about what to enforce and what not.

[victor-gonzalez]

I have been running a previous version (two days old) on a few of my source files and found two things so far which I guess haven't been modified

• I use process in the name of few functions and that requires all parameter being passed by reference, even int or float. I guess I should use the no lint directive in these lines
• I use using directives in a header but only inside of inline functions. Is this as well not recommended

Thanks @vkucera for the tremendous work!!!

[vkucera]

I have been running a previous version (two days old) on a few of my source files and found two things so far which I guess haven't been modified

* I use `process` in the name of few functions and that requires all parameter being passed by reference, even `int` or `float`. I guess I should use the `no lint` directive in these lines

* I use `using` directives in a header but only inside of `inline` functions. Is this as well not recommended

Thanks @vkucera for the tremendous work!!!

Hi @victor-gonzalez , thanks a lot for the testing and your report. Can you please send me links to the code in question so that I can have a look and see what the linter should do in those cases?

[vkucera]

@ddobrigk Ready to go!

[ddobrigk]

Merging following also discussion on Monday the 25th November. Thanks @vkucera !