Implement private modules

[Akirathan]

Created from discussion #7088.

This is the first step of the implementation of the private keyword. Let's start with private modules.

Note that private and project-private are synonyms.

### Tasks
- [x] Parser handles `private` keyword at the beginning of the module.
- [x] Ensure that private modules cannot be accessed outside the defining project. Neither via imports during compilation time, neither via FQN during runtime.

[jdunkerley]

We should allow a flag to enable bypassing this from the unit testing world as well please.

[Akirathan]

We should allow a flag to enable bypassing this from the unit testing world as well please.

Yes. That is mentioned in the linked discussion under Overcoming encapsulation.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-13):

Progress: Looking into the Rust parser - add private keyword. It should be finished by 2023-09-22.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-18):

Progress: - Catching up

• Book club
• Looking into the rust parser macros and trying to implement the private keyword It should be finished by 2023-09-22.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-19):

Progress: - Discussion with Kaz about the parser modifications

• Will implement all thhe rules for private keyword into the parser.
• Still getting familiar with the parser code base.
• Adding a new built in macro to the parser. It should be finished by 2023-09-22.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for yesterday (2023-09-20):

Progress: - Trying to implement a simple syntax rule for the private keyword - it is either standalone or followed by an identifier.

• Gave that out after a while - private is just a single token for now. Should be sufficient. It should be finished by 2023-09-22.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-21):

Progress: - Discussion with Hubert and Michal about some CI improvements - reordering of steps in the engine pipeline and disabling dry-run benchmarks on Mac and Windows

• Adding tests for private modules - ability to import projects from a sibling directory helps a lot with that.
• Struggling a bit with calling Scala stuff from Java.
• Implemented a functional prototype of PrivateModuleAnalysis compiler pass. It should be finished by 2023-09-22.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-22):

Progress: - More specification about parent module and sub module relationship with privacy

• It seems that a single compiler pass will not be sufficient, I might need to tweak the exports resolution such that it does not include private submodules into exportedSymbols. It should be finished by 2023-09-22.

[enso-bot[bot]]

Pavel Marek reports a new 🔴 DELAY for today (2023-09-25):

Summary: There is 7 days delay in implementation of the Implement private modules (#7304) task. It will cause 7 days delay for the delivery of this weekly plan.

Delay Cause: The implementation got a bit more complicated than I originally expected.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-25):

Progress: - I will need to modify BindingsMap after all - it is not sufficient to have just one independent compiler pass.

• Moreover, I might need to introduce PrivateAccessCheck at runtime, since I am struggling to properly implement access to a private module via FQN only in compile time.
• Created PRs for enabling asserts in Enso integration tests and for introduction of Enso-specific assert It should be finished by 2023-09-29.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-26):

Progress: - Looking into an inspiration for runtime access checks from FastR, graal-py and graal-js.

• Fix some PR reviews. It should be finished by 2023-09-29.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-27):

Progress: - Experimenting with checking accessibility of methods/types at runtime. It should be finished by 2023-09-29.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for today (2023-09-29):

Progress: - Trying to properly ensure that submodule hierarchy has same visibility.

• Seems that I cannot do that in a compiler pass, but will have to hack into Exports resolver. It should be finished by 2023-09-29.

[enso-bot[bot]]

Pavel Marek reports a new 🔴 DELAY for yesterday (2023-10-01):

Summary: There is 5 days delay in implementation of the Implement private modules (#7304) task. It will cause 5 days delay for the delivery of this weekly plan.

Delay Cause: Reverting back the runtime checks.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for yesterday (2023-10-01):

Progress: - Simplifying the compiler pass

• The submodule tree check is done also in the compiler pass.
• Almost merged. It should be finished by 2023-10-04.

[enso-bot[bot]]

Pavel Marek reports a new STANDUP for yesterday (2023-10-03):

Progress: - Fighting with the CI

• Talking about various improvements to the bench framework. It should be finished by 2023-10-04.