Bugfix/fix old tf architectures

[KaleabTessera]

What?

• Fix state based, networked and centralised architectures.
• Remove lp as independent dependency. It is a core dependency in acme, so for now, it is auto-downloaded with acme.
• Updated some core libraries.
• Change env_states to s_t for consistency.
• There is still a weird bug that occurs when running tests with shared_weights=False with multiple other tests. Full description of bug:

  Running tests with shared_weights=False pass when running indepedently
              (other tests commented out), but fail when run with other tests and not
              enough parallel cores (fail with 2 or less cores, pass with 4 cpu cores). This is likely a race condition,
              hangling process from previous tests or related to network sampling
              (TODO @Dries investigate if you have a chance). Only the test fails,
              the examples run.
  

  For now, I don't think it worth fixing these kind of tests since tf will be deprecated soon.

Why?

• So that tests pass and we can do final tf release.

How?

Extra

[mmorris44]

Looks good @KaleabTessera. Merge pending benchmarks.

Also, I had a few minor comments which you may choose to address if you'd like.

[RuanJohn]

Thank you @KaleabTessera! Benchmarks show no system performance degrading.