Implement exclusion of rules for the check results

Related to https://github.com/WordPress/plugin-check/issues/769

In actual this is more advanced form of above issue.

For application of PCP checks to the existing plugin in the directory, we need a mechanism for excluding certain error codes in certain files or directories. This is required because it is not possible to apply all PCP rules to the existing plugins without breaking those.

Few cases:

1. Exclude single error code in general:

Example:

mismatched_plugin_name

2. Exclude error code in certain files:

Example:

PluginCheck.CodeAnalysis.Offloading
-  /folder-one/file-1.php
-  /folder-one/file-2.php
-  /folder-two/sub-folder/file-2.php

3. Exclude error code in certain folders:

Example:

PluginCheck.CodeAnalysis.Offloading
-  /folder-one/
-  /another-folder/sub-folder/

4. Excluding could also be combination of 2 and 3.

Example:

PluginCheck.CodeAnalysis.Offloading
-  /folder-one/file-1.php
-  /folder-another/
-  /folder-two/sub-folder/

A set of rules would be assigned for each plugin which will be reviewed and approved by the reviewer manually.

Issue is here for tracking and gathering ideas and feedbacks regarding the implementation.

Questions:

1. In what format will we keep these rules?
2. How to make rules extendable and future-proof?
3. How will CLI/admin take these rules in the processing of the output?

Start by reviewing related issue #769 and the exclusion examples in this issue. Done would require an agreed, extendable rule format plus a defined way for CLI or admin processing to apply those exclusions; no implementation files or tests are identified yet.