Use LaTeX file list in project detection

[pfoerster]

Adds a parser for the .fls file that lists the working directory and all files processed during compilation. This can aid as a fallback when the regular syntax-based project detection fails due to macro definitions.

Fixes #1145.

[clason]

For larger projects, this can lead to a significant regression in startup time (I have one with a ~2300 line .fls file, for which texlab now needs ~25s to spin up where it was near instant (<1s) before -- on the same project!)

Can this be enabled conditionally, or made opt-in/out?

[pfoerster]

@clason Does #1164 restore the original startup time?

[clason]

Yes, it does, thank you!

(For the record, I'd be fine with it being opt-out; I suspect that projects such as this are the exception rather than the rule -- although probably not so rare.)

[pfoerster]

For the record, I'd be fine with it being opt-out; I suspect that projects such as this are the exception rather than the rule -- although probably not so rare.

For now, I'd rather keep it fast and enable it by default once it's fast enough that it doesn't impact performance (that much).