fix(manager/gradle): qGroovySingleMapOfVarAssignment and qGroovyMapOfExpr str format var name support

[panaglev]

Changes

Fixed qGroovySingleMapOfVarAssignment and qGroovyMapOfExpr which can now handles string variables format.
Supported format before:

 project.ext.versions = [
            some: invalidsymbol,
            android: [
              buildTools: '30.0.3'
            ],

After changes might also support comma-defined variables:

 project.ext.versions = [
            'some': invalidsymbol,
            'android': [
              'buildTools': '30.0.3'
            ],

Sort of continuation of this pull request feat(manager/gradle): add support for Groovy and Kotlin maps #19127

Context

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[renovate-release]

🎉 This PR is included in version 39.191.2 🎉

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• npm package (@latest dist-tag)
• 39.191.2

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