fix(templates): the BPM starter's form calls its client-Java service

[delchev]

Fixes red master nightly

BPMStarterTemplateIT is failing on master on both the H2 and the PostgreSQL leg.

#6619 migrated the BPM starter's two TypeScript files to client Java but left everything that talks
to them pointing at the retired TypeScript, so the sample does not work at all:

• The form posted to /services/ts/<project>/api/ProcessService.ts/processes — a file that PR deleted
  — and branched on response.status != 202, the status the TS service used to set, where the
  client-Java @Controller answers 200. That is the failure the nightly reports: the alert reads
  Unable to trigger a new process: 'undefined', because the error branch prints response.message,
  which the form-builder's $http shim never sets. It now posts to
  /services/java/<project>/<javaPackageName>/ProcessService/processes and uses a proper error
  callback instead of an exact-status branch, which also gives the failure path a real message.
• The service task logged a different line than before the migration (Process instance [id] with variables vs Process variables), which the test asserts. Restored, so the sample's observable
  behaviour is unchanged by the port.

The test itself also watched the wrong logger: console.log from the retired TypeScript landed on
app.out, while the SDK logger nests the given name under app., so the Java task logs to
app.<package>.MyServiceTask — which an appender bound to app.out never sees, and which
logback-test.xml pins to ERROR. It now watches the app tree, so it observes any client-application
log and does not depend on the package name derived from the project.

Verified locally by the commit's author: the process starts through the Java controller and the task
logs app.bpmtestproject.MyServiceTask - Hello World! Process variables: {param1=string-param-value, param2=777.0}.

Full rationale is in the commit message.

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