improvement: Make including detail in completion label configurable

[Sorixelle]

Some LSP clients (such as Emacs using Eglot and Corfu) use the label field to insert a completion if completionItem/resolve has not returned by the time the completion is selected. Including the contents of the detail property in the label causes it to be included in the file itself in these clients. To remedy this, we define a isDetailIncludedInLabel option under compilerOptions to make this behaviour toggleable. We also disable this behaviour by default in Emacs, since this is where the undesirable behaviour was located.

TODO:

• Figure out why option is ignored in Scala 3.3.4 projects
• Testing (unsure what tests should be added - please let me know where they should go)

Fixes #6849.

[Sorixelle]

Seems like the changes to MetalsServerConfig.default don't get applied to Scala 3.3.4 projects. Tested with a Mill project using 3.3.4 and the option is not automatically applied - I need to configure my editor to set it explicitly during the initialize command. Bad test case on my end, it seems like the option is not honored at all in 3.3.4. Unsure why this is the case - any pointers?

EDIT: Some investigation leads me to believe that Metals is falling back to the Scala presentation compiler instead of mtags. Unsure if there's anything that can be done about that until mtags is updated for 3.3.4.

[tgodzik]

EDIT: Some investigation leads me to believe that Metals is falling back to the Scala presentation compiler instead of mtags. Unsure if there's anything that can be done about that until mtags is updated for 3.3.4.

From 3.3.4 onwards we use mtags published by the compiler itself to avoid having to publish it to every version of the compiler.

[tgodzik]

Ach, and we usually just port them ourselves, so no need to worry about it

[tgodzik]

Looks good aside from the MiMa failure 🎉

[Sorixelle]

Addressed the default - are we sure this change doesn't require any tests? I'd add them, I'm just not sure where they belong.