Guard rails around collect/parallelize

**Is your feature request related to a problem? Please describe.**
There are a few edge cases that aren't handled in the code:
1. One tries to query for a node within a block between `Parallelizable[]`/`Collect` https://github.com/DAGWorks-Inc/hamilton/issues/1029
2. One passes or overrides nodes for ^^^
3. A `Parallelizable` directly preceeding a `Collect`
4. A `Parallelizable` with no `Collect` coming afterwards
5. A `Parallelizable` with multiple `Collect`s -- this should be allow eventually but its not feasible now. See https://github.com/DAGWorks-Inc/hamilton/issues/742.
6. Multiple `Collect` in a node
7. No nodes in between `Parallelizable` and `Collect` - https://github.com/DAGWorks-Inc/hamilton/issues/1030

And probably a few more.

**Describe the solution you'd like**
Clean errors as early as possible. Currently this does nothing.
**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**

Follow up from this: https://github.com/DAGWorks-Inc/hamilton/pull/299.