Make it easier for users to change build server's memory requirements

[tgodzik]

When Metals runs it actually starts 2 processes. One is the server itself and the other is the build server (either Bloop or sbt). This is not always clear to the users and they might be surprised by a rouge process taking up a lot of their memory.

I propose that we expose metals.buildServerProperties similar to metals.serverProperties that would modify the proper json file (.bloop/bloop.json or .bsp/sbt.json) and then show a message to restart the server. This way users will not need to dig in the Bloop docs to find what they need to do.

Changing automatically someones bloop.json files is not perfect, but honestly I don't see any other solution here. And we can easily append to existing options.

Also, we could use the Metals javaHome for Bloop if it's not already set there.

We can add a warning to the setting, that it will modify a file on disk and give them a link to it?

Additional context

scalameta/metals-vscode#204

Search terms

bloop bsp memory sbt server