Language Injections: merge the escaping methods

[ForNeVeR]

Currently, we have two main string escape mechanisms used when editing the injected language fragments: com.intellij.plugin.powershell.lang.util.PowerShellStringUtil#escapeStringCharacters and com.intellij.plugin.powershell.ide.injection.PowerShellStringManipulator#escapeQuotes. Near the latter, there's a comment suggesting to merge them both in one function.

We should consider that.

See the code near this line:

intellij-powershell/src/main/kotlin/com/intellij/plugin/powershell/ide/injection/PowerShellStringManipulator.kt

Line 66 in baccc65

//todo implement in PowerShellStringUtil.escapeStringCharacters()

Also, look for the number of this issue in the project code base.