Support Kotlin for public beta

[angelapwen]

Kotlin will enter public beta with the release of 2.11.4. This change:

• adds it to the list of languages that a user could specify in the init action, aliasing it to Java.
• checks in Kotlin test code and a Kotlin build command to our test custom build, so that its extraction and autobuild will be tested along with existing Kotlin tests
• adds support for a feature flag, disable_kotlin_analysis_enabled, that will allow us to mass-enable the CODEQL_EXTRACTOR_JAVA_AGENT_DISABLE_KOTLIN flag (ie. disable Kotlin extraction). The flag is not yet implemented on github.com so the code is a no-op at the moment.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Confirm the readme has been updated if necessary.
• Confirm the changelog has been updated if necessary.

[adityasharad]

Nice. Thank you for looking into this!

[angelapwen]

I decided to remove the PR check that tests that when the CODEQL_EXTRACTOR_JAVA_AGENT_DISABLE_KOTLIN option is passed to the CLI, analysis will fail — when it's disabled, our Java analysis actually is able to still run off of the Java test code checked in. I think it's probably not necessary to test here as it should be tested in the CLI.

[henrymercer]

An optional comment, otherwise LGTM

[angelapwen]

I am updating the feature flag name to include _cli because the code scanning experiences team has another similar-sounding Kotlin feature flag in the monolith repo. Sorry, needs re-review again!