note in validator guide about slashing and exit operation interaction

[djrtwo]

addresses #2084.

• add note about the interaction between slashings and voluntary exits of the same index in the same block
• add block tests for a few conditions

note added new test_multi_operation.py testfile that outputs block tests. We are lacking in interesting/complex block tests with operations of multiple/many types. I plan to add a number of tests here in the following week

[hwwhww]

An issue of the test format, otherwise LGTM!

[lucianyao]

Hi @hwwhww , I have seen it was committed to v1.0-candidate, while the default is the dev, I would like to know which branch is the canonical spec for implementer to follow?thanks!

[hwwhww]

@lucianyao They both are.

• v1.0-candidate is the branch for the incoming spec v1.0.0, now only accepts critical fixes or test vector updates.
• dev is currently serving the non-phase-0-launch PRs. e.g., phase 1 specs
• master is the release tags branch.

I suppose @djrtwo will merge v1.0-candidate into master and cut 1.0.0, and then backport master to dev. If you're finding phase 0 issues, I suggest you look at v1.0-candidate branch. Thank you! :)