Update RedundantVisibilityModifierRule to find redundant internal modifiers

[3flex]

There were some redundant internal modifiers identified by the IDE that weren't picked up by detekt's own rule, so I updated the rule to find this type of usage.

I also enabled the rule for detekt self-scans and fixed the reported issues.

[codecov]

Codecov Report

Merging #3092 into master will decrease coverage by 0.00%.
The diff coverage is 76.92%.

@@             Coverage Diff              @@
##             master    #3092      +/-   ##
============================================
- Coverage     79.28%   79.27%   -0.01%     
- Complexity     2577     2579       +2     
============================================
  Files           435      435              
  Lines          7766     7774       +8     
  Branches       1482     1484       +2     
============================================
+ Hits           6157     6163       +6     
  Misses          819      819              
- Partials        790      792       +2     

Impacted Files	Coverage Δ	Complexity Δ
...n/io/github/detekt/metrics/processors/util/LLOC.kt	73.33% <ø> (ø)	3.00 <0.00> (ø)
...rbosch/detekt/rules/complexity/NestedBlockDepth.kt	91.83% <66.66%> (ø)	5.00 <0.00> (ø)
...ekt/rules/style/RedundantVisibilityModifierRule.kt	95.45% <77.77%> (-4.55%)	9.00 <2.00> (+2.00)	⬇️
...bosch/detekt/rules/bugs/EqualsWithHashCodeExist.kt	88.88% <100.00%> (ø)	8.00 <0.00> (ø)

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