There are two projects transitively required by `runtime`, that have akka dependencies:
- `downloader`
- `connected-lock-manager`
This PR replaces the `akka-http` dependency in `downloader` by HttpClient from JDK, and splits `connected-lock-manager` into two projects such that there are no akka classes in `runtime.jar`.
# Important Notes
- Simplify the `downloader` project - remove akka.
- Add HTTP tests to the `downloader` project that uses our `http-test-helper` that is normally used for stdlib tests.
- It required few tweaks so that we can embed that server in a unit test.
- Split `connected-lock-manager` project into two projects - remove akka from `runtime`.
- **Native image build fixes and quality of life improvements:**
- Output of `native-image` is captured 743e167aa4
- The output will no longer be intertwined with the output from other commands on the CI.
- Arguments to the `native-image` are passed via an argument file, not via command line - ba0a69de6e
- This resolves an issue on Windows with "Command line too long", for example in https://github.com/enso-org/enso/actions/runs/7934447148/job/21665456738?pr=8953#step:8:2269
Upgrade to GraalVM JDK 21.
```
> java -version
openjdk version "21" 2023-09-19
OpenJDK Runtime Environment GraalVM CE 21+35.1 (build 21+35-jvmci-23.1-b15)
OpenJDK 64-Bit Server VM GraalVM CE 21+35.1 (build 21+35-jvmci-23.1-b15, mixed mode, sharing)
```
With SDKMan, download with `sdk install java 21-graalce`.
# Important Notes
- After this PR, one can theoretically run enso with any JRE with version at least 21.
- Removed `sbt bootstrap` hack and all the other build time related hacks related to the handling of GraalVM distribution.
- `project-manager` remains backward compatible - it can open older engines with runtimes. New engines now do no longer require a separate runtime to be downloaded.
- sbt does not support compilation of `module-info.java` files in mixed projects - https://github.com/sbt/sbt/issues/3368
- Which means that we can have `module-info.java` files only for Java-only projects.
- Anyway, we need just a single `module-info.class` in the resulting `runtime.jar` fat jar.
- `runtime.jar` is assembled in `runtime-with-instruments` with a custom merge strategy (`sbt-assembly` plugin). Caching is disabled for custom merge strategies, which means that re-assembly of `runtime.jar` will be more frequent.
- Engine distribution contains multiple JAR archives (modules) in `component` directory, along with `runner/runner.jar` that is hidden inside a nested directory.
- The new entry point to the engine runner is [EngineRunnerBootLoader](https://github.com/enso-org/enso/pull/7991/files#diff-9ab172d0566c18456472aeb95c4345f47e2db3965e77e29c11694d3a9333a2aa) that contains a custom ClassLoader - to make sure that everything that does not have to be loaded from a module is loaded from `runner.jar`, which is not a module.
- The new command line for launching the engine runner is in [distribution/bin/enso](https://github.com/enso-org/enso/pull/7991/files#diff-0b66983403b2c329febc7381cd23d45871d4d555ce98dd040d4d1e879c8f3725)
- [Newest version of Frgaal](https://repo1.maven.org/maven2/org/frgaal/compiler/20.0.1/) (20.0.1) does not recognize `--source 21` option, only `--source 20`.
