[CBR-207] Remove log warper dependency

[365andreas]

Description

In total 163 source code files import ‘System.Wlog’ directly from ‘log-warper’ and 16 modules in cardano-sl link to this library (as indicated in their cabals). We want to reduce the dependency on this external library.

As a first step we introduce module ‘Pos.Util.Wlog’ in ‘util’ that exports all of ‘System.Wlog’ and change the import statement in all 163 source files.

This way we can get rid of the direct dependency on ‘log-warper’ in ‘cardano-sl’ modules and only refer to it from module ‘util’.

Linked issue

https://iohk.myjetbrains.com/youtrack/issue/CBR-207

Type of change

• [~] 🐞 Bug fix (non-breaking change which fixes an issue)
• [~] 🛠 New feature (non-breaking change which adds functionality)
• [~] ⚠️ Breaking change (fix or feature that would cause existing functionality to change)
• 🏭 Refactoring that does not change existing functionality but does improve things like code readability, structure etc
• [~] 🔨 New or improved tests for existing code
• [~] ⛑ git-flow chore (backport, hotfix, etc)

Developer checklist

• I have read the style guide document, and my code follows the code style of this project.
• If my code deals with exceptions, it follows the guidelines.
• I have updated any documentation accordingly, if needed. Documentation changes can be reflected in opening a PR on cardanodocs.com, amending the inline Haddock comments, any relevant README file or one of the document listed in the docs directory.
• [~] CHANGELOG entry has been added and is linked to the correct PR on GitHub.

Testing checklist

• [~] I have added tests to cover my changes.
• All new and existing tests passed.

QA Steps

Screenshots (if available)

[CodiePP]

this abstracts 'log-warper' such that the direct import of it in other cardano-sl modules can be removed.

[erikd]

LGTM!