Reorganize docs for the configuration file

[chao2zhang]

• failonbuild.md does not need to live on a standalone page, it is too short and it is mentioned at configurations.md:12 already.
• Remove obsolete information and improve the wording overall.
• Break long lines when they exceed the line length hint too much.
• As mentioned in Support configurable severity per ruleset/rule in XML and Sarif output #3310, I removed the legacy severity of the generated documentation for rules. I will need to update Support configurable severity per ruleset/rule in XML and Sarif output #3310 based on this PR.

Fun fact: Some of the new discussions like #3279 (comment) are already documented in the Path Filters / Excludes / Includes section.

[codecov]

Codecov Report

Merging #3337 (a4c3af0) into master (ff655d2) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #3337      +/-   ##
============================================
- Coverage     80.34%   80.27%   -0.08%     
+ Complexity     2724     2718       -6     
============================================
  Files           445      445              
  Lines          8177     8239      +62     
  Branches       1555     1563       +8     
============================================
+ Hits           6570     6614      +44     
- Misses          774      785      +11     
- Partials        833      840       +7     

Impacted Files	Coverage Δ	Complexity Δ
...enerator/printer/rulesetpage/RuleSetPagePrinter.kt	86.84% <ø> (-0.97%)	16.00 <0.00> (-2.00)
...ain/kotlin/io/gitlab/arturbosch/detekt/api/Rule.kt	82.60% <0.00%> (-17.40%)	16.00% <0.00%> (+1.00%)	⬇️
...in/kotlin/io/gitlab/arturbosch/detekt/api/Issue.kt	75.00% <0.00%> (-12.50%)	4.00% <0.00%> (-1.00%)
...io/github/detekt/report/sarif/SarifOutputReport.kt	90.62% <0.00%> (-9.38%)	4.00% <0.00%> (ø%)
...kotlin/io/gitlab/arturbosch/detekt/api/Findings.kt	62.50% <0.00%> (-8.93%)	0.00% <0.00%> (ø%)
...lin/io/github/detekt/report/xml/XmlOutputReport.kt	91.30% <0.00%> (-4.85%)	7.00% <0.00%> (-2.00%)
.../main/kotlin/io/github/detekt/parser/KtCompiler.kt	81.81% <0.00%> (-4.55%)	8.00% <0.00%> (+1.00%)	⬇️
...h/detekt/core/baseline/IndentingXMLStreamWriter.kt	58.82% <0.00%> (-1.56%)	14.00% <0.00%> (-1.00%)
...o/gitlab/arturbosch/detekt/internal/SharedTasks.kt	60.86% <0.00%> (-1.04%)	0.00% <0.00%> (ø%)
...otlin/io/gitlab/arturbosch/detekt/api/CodeSmell.kt	59.57% <0.00%> (-0.90%)	13.00% <0.00%> (+2.00%)	⬇️
... and 24 more

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[schalkms]

Suggested change

	_detekt_ supports the option to fail your build if a threshold of code smell issues is met.
	_Detekt_ supports the option to fail your build if a threshold of code smell issues is met.

[chao2zhang]

We have a mix and match of Detekt and detekt across the documentation and README.md though, have we agreed upon preferring Detekt?

[schalkms]

Not sure though. However, this is the beginning of a sentence. Hence, it starts with one capital letter.