Just: introduce common "verbs"

[redsun82]

This introduces common "verbs" (build, test, format, lint, generate) that individual parts of the project can implement, and shared infrastructure in misc/just/ to support them.

Forwarding

The core of the functionality is given by forwarding. The idea is that:

• if you are in the directory where a verb is implemented, you will get that as per standard just behaviour (possibly using fallback).
• if on the other hand you are above it, and you run something like just test ql/rust/ql/test/{a,b}, then a forwarder script finds a common justfile implementing the verb for all the positional arguments passed there, and then retries calling just test from there. So if test is implemented beneath that (in that case, it is in rust/ql/test), it uses that recipe.
• even if there isn't a recipe that is common to all the positional arguments, the forwarder will still group the arguments in batches using the same recipe. So just build ql/rust ql/java, or just test ql/rust/ql/test/some/language/test ql/rust/ql/integration-test/some/integration/test will also work, with corresponding recipes run sequentially.

Running QL tests

How launching QL tests can be tweaked:

• by default, the corresponding CLI is built from the internal repo (nothing is done if working in codeql standalone), and no additional database or consistency checks are made
• --codeql=built can be passed to skip the build step (if no changes were made to the CLI/extractors). This is consistent with the same pytest option
• you can add the additional checks that CI does with --all-checks or the + abbreviation. These additional checks are configured in justfiles per language, and correspond to all the additional checks that CI adds (but that a dev might not want to run by default).

What this PR does

Adds shared just infrastructure (misc/just/)

• defs.just: core verb definitions and helpers
• forward.just / forward_command.py: forwarding mechanism to dispatch verbs from any directory
• language_tests.py / codeql_test_run.py: Python helpers for running codeql test run with the right options
• build.just / format.just / lib.just: shared recipes for building, formatting, and common settings
• semmle-code-stub.just: stubs for internal-repo-specific settings when working standalone
• README.md: documentation for the whole system

Adds per-language justfiles

Each language (actions, cpp, csharp, go, java, javascript, python, ruby, rust, swift) gets:

• a top-level <lang>/justfile importing the shared infrastructure
• <lang>/ql/justfile and <lang>/ql/test/justfile for QL tests
• <lang>/ql/integration-tests/justfile for integration tests

Moves C++ consistency queries

semmlecode-cpp-consistency-queries/ → cpp/ql/consistency-queries/ (these were in the internal repo only, but belong here).

Other changes

• Adds codegen support (notably for rust)
• Adds root justfile and lib.just for top-level verb dispatch
• Upgrades the just binary and modernizes justfile syntax

Caveats

• Passing arguments with spaces generally doesn't work, although setting arguments with spaces in justfiles (for the base arguments) is supported using escaping as in \\ . This is a known limitation of just (see Question: How to forward *args? casey/just#1988)
• When running different recipes for the same verb, non-positional arguments need to be supported by all recipes involved. For example, this will work ok for --learn or --codeql options in language and integration tests

Companion PR

The internal repo companion PR ports all languages to use this new infrastructure and updates CI accordingly.

[redsun82]

Superseded by #22576, which has the same content on a history that can be reviewed commit by commit, rebased on current main.

The substantive difference is that it uses set lists for recipe arguments, now that casey/just#1988 is fixed, instead of encoding them as whitespace-separated strings. That encoding turned out to be lossy in two ways this hit in practice.