Rapid test ensure bitstream consumed

[VenelinMartinov]

[rapid] flaky test, can not reproduce a failure
        Traceback (group did not use any data from bitstream; this is likely a result of Custom generator not calling any of the built-in generators):

rapid wants us to always consume from the random bitstream but we don't do that when we generate empty collection values. This just adds some generators in those cases so that rapid doesn't panic.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 60.77%. Comparing base (2094289) to head (cf0801e).

Files	Patch %	Lines
pkg/tests/cross-tests/rapid_tv_gen.go	0.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2013 +/- ## ======================================= Coverage 60.76% 60.77% ======================================= Files 350 350 Lines 45686 45689 +3 ======================================= + Hits 27762 27766 +4 Misses 16405 16405 + Partials 1519 1518 -1 ```

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[iwahbe]

@VenelinMartinov Do we want to merge this?

[VenelinMartinov]

I've meant to revisit but haven't managed to yet. If you are seeing the panics here then I'm happy to merge this until we find time to root-cause

[iwahbe]

I've meant to revisit but haven't managed to yet.

No problem.

If you are seeing the panics here then I'm happy to merge this until we find time to root-cause

I'm not sure what you mean here.

[VenelinMartinov]

I'm not sure what you mean here.

Are you blocked on this PR getting merged or were you just revisiting old PRs?

[iwahbe]

I'm not sure what you mean here.

Are you blocked on this PR getting merged or were you just revisiting old PRs?

Just revisiting old PRs.