NullableToStringCall: fix false negative in lambda

[t-kameyama]

Fixes #6349
Fixes #6378

[codecov]

Codecov Report

Merging #6352 (e256278) into main (d1b3e53) will increase coverage by 0.03%.
Report is 34 commits behind head on main.
The diff coverage is 76.92%.

@@             Coverage Diff              @@
##               main    #6352      +/-   ##
============================================
+ Coverage     85.13%   85.17%   +0.03%     
+ Complexity     4032     4005      -27     
============================================
  Files           571      570       -1     
  Lines         13432    13387      -45     
  Branches       2373     2354      -19     
============================================
- Hits          11436    11403      -33     
+ Misses          837      834       -3     
+ Partials       1159     1150       -9     

Files Changed	Coverage Δ
...turbosch/detekt/rules/bugs/NullableToStringCall.kt	89.65% <76.92%> (+0.46%)	⬆️

... and 25 files with indirect coverage changes

[atulgpt]

HI @t-kameyama you beat me in fixing this issue 🤣

in my fix(at commit) I changed your method as below

private fun KtExpression.targetExpression(): KtExpression? {
    val qualifiedExpression = getStrictParentOfType<KtQualifiedExpression>()
    return if (this.parent is KtStringTemplateEntry) {
        this
    } else if (qualifiedExpression != null) {
        qualifiedExpression.takeIf { it.selectorExpression == this } ?: return null
    } else {
        null
    }
}