Added support for multiple frontend instances and a single Skyline server

[michaelshin]

• Refactored Skyline so an entry point is not required to launch Skyline.
• Added the entry point and project root as part of the initialization request message and saved the entry point/project root for each connection

[jimgao1]

Generally looks good to me!

However, we might want to have some mutual exclusion mechanism to ensure that only one profiling session can be executing at any given time. This is to ensure that we don't get interference from runtime (i.e. two models running together slowly) or memory (i.e. if it OOMs).

[michaelshin]

The ThreadPoolExecutor that actually runs the profile only has one worker so I believe we do not need to add an additional mutual exclusion mechanism. Do you think this is sufficient?

[jimgao1]

Looks good!