Add `--tags=$TAG1,$TAG2`

[bphenriques]

Hello,

In my use-case I want to have two set of integration tests:

1. Ones that I can run entirely locally. Not tags set.
2. Others that require connecting to a real testing environment. Tests tagged with uat-integration.

Given that 2. has a non-trivial local setup, I want to exclude those tags by default from the tests:

IntegrationTest / testOptions += Tests.Argument("--exclude-tags=uat-integration"),

Now, if I want to run them on-demand, I would like to run as follows:

$ sbt "it:testOnly -- --include-tags=uat-integration