Introduce `RedundantStringEscape` check

[Stephan202]

Suggested commit message:

Introduce `RedundantStringEscape` check (#1138)

This check aims to simplify string constants by dropping redundant
single quote escape sequences. The check is optimized for performance.

While there, update existing checks such that they do not introduce
violations of the type flagged by this new check.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
98.2% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[github-actions[bot]]

• Surviving mutants in this change: 1
• Killed mutants in this change: 31

class	surviving	killed
:zombie:tech.picnic.errorprone.bugpatterns.RedundantStringEscape	1	21
:tada:tech.picnic.errorprone.utils.SourceCode	0	5
:tada:tech.picnic.errorprone.bugpatterns.StringJoin	0	1
:tada:tech.picnic.errorprone.bugpatterns.Slf4jLogStatement	0	2
:tada:tech.picnic.errorprone.guidelines.bugpatterns.ErrorProneRuntimeClasspath	0	2

Mutation testing report by Pitest. Review any surviving mutants by inspecting the line comments under Files changed.