* ENT-11387: Fix to prevent interleaved stop/start causing bridge to be started with null session.
* ENT-11387: Fixed bug in assigning null to session.
* It uses URLs when in fact CorDapps are jar files, and so should being Path. It also does URL equality, which is not recommended
* Address (very old) TODO of removing RestrictedURL, which is not needed
Also, back-ported some minor changes from https://github.com/corda/enterprise/pull/5057.
The node now sends a transaction to the verifier if any of its attachments were compiled with Kotlin 1.2 (the net.corda.node.verification.external system property has been removed). It uses kotlinx-metadata to read the Kotlin metadata in the attachment to determine this. For now this scanning is done each time the attachment is loaded from the database.
The existing external verification integration tests were converted into smoke tests so that 4.11 nodes could be involved. This required various improvements to NodeProcess.Factory. A new JAVA_8_HOME environment variable, pointing to JDK 8, is required to run these tests.
There is still some follow-up work that needs to be done:
Sending transactions from a 4.11 node to a 4.12 node works, but not the other way round. A new WireTransaction component group needs to be introduced for storing 4.12 attachments so that they can be safely ignored by 4.11 nodes, and the 4.12 node needs to be able to load both 4.11 and 4.12 versions of the same contracts CorDapp so that they can be both attached to the transaction.
Even though attachments are cached when retrieved from the database, the Kotlin metadata version should be stored in the attachments db table, rather than being scanned each time.
Finally, VerificationService was refactored into NodeVerificationSupport and can be passed into SignedTransaction.verifyInternal, instead of needing the much heavier VerifyingServiceHub. This makes it easier for internal tools to verify transactions and spawn the verifier if necessary.
This requires Kotlin 1.2 versions of core and serialization (core-1.2 and serialization-1.2 respectively), which are just "shell" modules and which compile the existing source code with Kotlin 1.2. The 1.2 plugin does not work with the current version of Gradle and so the 1.2 compiler has to be called directly.
Now with two versions of Kotlin in the code base, each module needs to have its version manually specified to ensure a clean separation. Otherwise, the default Kotlin version can override 1.2 when needed.
Some of the code was tidied-up or improved to enable it to be cross-compiled. For post-1.2 APIs being used, they have been copied into core-1.2 with the same method signatures. OpenTelemetryComponent was moved to node-api, along with the dependency, to avoid also having a 1.2 version for the opentelemetry module.
