Add randomized tests for adding/removing keys

[Manav-Aggarwal]

Overview

We'd like to add randomized tests for Set and Remove that add new keys and delete existing keys respectively. Mainly, we'd like to make sure that Deep Subtrees are constructed with all the data they might need to rebalance correctly when new keys are added or existing keys are removed.

Adds following tests:

[x] - Batch-add random keys.
[x] - Randomize both the operations, Set and Remove, and the keys they are operating on so calls to both are interleaved together in no particular order. Note that the tree should need various rebalances when doing the above operations.

Make sure the tree rebalances correctly at each stage (check against existing IAVL tree: mutable tree).

Overall, it adds strong substantial tests for an IAVL Deep Subtree.

Since this tests the Remove implementation, we can close out #14 as well.

Resolves: #15, resolves: #14

Checklist

• New and updated code has appropriate documentation
• New and updated code has new and/or updated testing
• Required CI checks are passing
• Visual proof for any user facing features like CLI or documentation updates
• Linked issues closed with keywords

[tzdybal]

I left some comments - mostly about simplifying the code. The tracing solution seems very clean 👍

[tzdybal]

I know it's just a test, but this function is huge and complex. Can we for example:

• extract key as a function, instead of using lambda?
• have separate helper functions for Set and Remove?
• probably introducing a struct with methods will make most sense (so we don't need to pass to many params)

[Manav-Aggarwal]

Could you please clarify "probably introducing a struct with methods will make most sense (so we don't need to pass to many params)" in the updated code?

[tzdybal]

Something like:

type testContext struct {
  r io.Reader
  tree *MutableTree
  dst *DeepSubTree
  keys set.Set[string]
}

func (tc *testContext) getKey(getRandom bool) ([]byte, error) {
// ...
}

func (tc *testContext) removeInDst(key []byte) error {
// ...
}

func (tc *testContext) setInDst([key, value []byte, isNewKey, isFirstKey bool) error {
// .... 
}

[Manav-Aggarwal]

Thanks, updated!