Enable Server gc

[nojaf]

On my local machine:

Before:

Benchmark/step-0> | Method |     Mean |   Error |  StdDev | Rank |       Gen0 |      Gen1 |     Gen2 | Allocated |
Benchmark/step-0> |------- |---------:|--------:|--------:|-----:|-----------:|----------:|---------:|----------:|
Benchmark/step-0> | Format | 136.0 ms | 0.55 ms | 0.46 ms |    1 | 13250.0000 | 2500.0000 | 750.0000 | 157.83 MB |

After:

Benchmark/step-0> | Method |     Mean |    Error |   StdDev | Rank |     Gen0 |     Gen1 | Allocated |
Benchmark/step-0> |------- |---------:|---------:|---------:|-----:|---------:|---------:|----------:|
Benchmark/step-0> | Format | 98.23 ms | 0.772 ms | 0.722 ms |    1 | 600.0000 | 400.0000 | 157.82 MB |

I think we should do this for the daemon as well, as this makes sense for the request/response model of an LSP.
FsAutoComplete does this as well.