Improve deep clone performance

[louiszawadzki]

What does this PR do?

Improve the performance of the deep clone function that is used for event mappers.

If we need to increase the depth of clones again, we can also look at dropping some keys from the clone: for the actionEventMapper, what takes a lot of cloning time is the actionContext containing a lot of circular references.
Dropping this field from the cloned object would also significantly reduce the impact on performance, but is a bit less straightforward than just decreasing the max object depth.

Motivation

Currently adding an actionEventMapper slows apps down on user interactions: #514

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change

[justinadkins]

LGTM, thank your lightning fast response to this @louiszawadzki!

[justinadkins]

🔥

[justinadkins]

I did some sampling in our application and can confirm this resolves the performance hit. deepClone is now running <1ms on average. The largest I saw was 2.75ms.