Control which dependencies can be updated

[lukaszwawrzyk]

User should be able to specify list of allowed dependencies that should be updated (to opt in to bazel-steward for limited set of deps) and/or a list of ignored dependencies. As in all cases when specifying deps it should be possible to use some regex/wildcard to specify groups of libraries in a general way. Also it should be "scopable" to given platform like maven or python.

[lukaszwawrzyk]

Partially addressed in https://github.com/VirtusLab/bazel-steward/pull/243 It is possible to disable dependencies or whole kinds through enabled: false. Missing part is to implement enabled: true to only update given dependencies.