[BUG] [Spring] Open-Api code generator plugin fails to escape backslash character

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

Trying to generate a Java client from open api specification.

openapi-generator version

4.3.1

OpenAPI declaration file content or url

paths:
  /sources:
    $ref: 'paths.yaml#/~1sources'
  /sources/{directorySourceId}:
    $ref: 'paths.yaml#/~1sources~1{directorySourceId}'
  /sources/{directorySourceId}/actions:
    $ref: 'paths.yaml#/~1sources~1{directorySourceId}~1actions'

openApiGenerate {
        generatorName = "spring"
        outputDir = "$buildDir/openapi".toString()
        apiFilesConstrainedTo = [""]
        modelFilesConstrainedTo = [""]
        supportingFilesConstrainedTo = ["ApiUtil.java"]
        configOptions = [delegatePattern: true, dateLibrary: "java8", useTags: true]
        typeMappings = ["OffsetDateTime" : "Instant"]
        importMappings = ["java.time.OffsetDateTime" : "java.time.Instant"]
        validateSpec = true
    }

Steps to reproduce

./gradlew clean openApiGenerate

It causes error with

#/components/schemas/~1sources~1{directorySourceId} is not defined
#/components/schemas/~1sources~1{directorySourceId} is not defined
#/components/schemas/~1sources~1{directorySourceId} is not defined
~1sources~1{directorySourceId} (model name starts with number) cannot be used as model name. Renamed to Model1sources1directorySourceId

causing model names to be Model1sources1directorySourceId and Model1sources1directorySourceId1actions.

Related issues/PRs

Previous PR on older versions- 1691

Suggest a fix

This works fine with plugin version 4.2.0

Start with the reported ./gradlew clean openApiGenerate entry point, using the supplied OpenAPI paths and Spring configuration on generator version 4.3.1. Compare the generated model names with the expected escaped path names and verify behavior against version 4.2.0; done means generation completes without the reported undefined-schema errors or mangled model names.