ci: improve gitlint (max line length in body with exceptions)

Follow-up of 5aa1540c5d but way more
mature. We now use custom gitlint rules written in Python to better
handle the max line length, with respect to a few valid exceptions.
Recognizing code blocks or compiler output, as discussed, is not
trivial and hard to get right for all corner-cases. Therefore, this
commit is a pragmatic way forward. The CI job should be kept optional.

Allowed exceptions for the 72 line length limit are now:

1. links in the following three common patterns:
https://example.com/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links
[0] https://example.com/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links
[0]: https://example.com/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links/very-long-links

2. code blocks (anything between the three backticks)

```
let x = "very_long_very_long_very_long_very_long_very_long_very_long_very_long_very_long_very_long_very_long_"
```

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

.gitlint

@@ -1,6 +1,7 @@
 [general]
-extra-path=scripts/gitlint/rules.py
+extra-path=scripts/gitlint/rules
 regex-style-search=true
+ignore=body-max-line-length
 
 [ignore-by-author-name]
 regex=dependabot
@@ -10,11 +11,3 @@ ignore=all
 [title-max-length]
 line-length=72
 
-# default 80
-[body-max-line-length]
-line-length=72
-
-# Allow developers to add long links to useful resources
-[ignore-by-body]
-regex=^https?:\/\/
-ignore=body-max-line-length