Improve Deprecation and Documentation for allRules

[cortinico]

Fixes #3567

This PR adds:

• Documentation for the allRules property in the Gradle documentation page
• A Deprecation annotation on the allRules accessors in the extention an the tasks.
• More spacing in the Gradle config page as it's getting harder to read

[codecov]

Codecov Report

Merging #3596 (421934b) into main (c16ecf6) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #3596   +/-   ##
=========================================
  Coverage     77.53%   77.53%           
  Complexity     2835     2835           
=========================================
  Files           464      464           
  Lines          8779     8779           
  Branches       1720     1720           
=========================================
  Hits           6807     6807           
  Misses         1046     1046           
  Partials        926      926           

Impacted Files	Coverage Δ	Complexity Δ
.../main/kotlin/io/gitlab/arturbosch/detekt/Detekt.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)
...tlab/arturbosch/detekt/DetektCreateBaselineTask.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)
...ab/arturbosch/detekt/extensions/DetektExtension.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c16ecf6...421934b. Read the comment docs.