Workaround for new Chrome limit on message size

[zalmoxisus]

As discussed in #566 and #543, Chrome added a limit on messages, so we're splitting bigger object parts into chunks. However by increasing the sate, the extension will have out-of-memory crash at some point, so in future versions we need an option to run devtools from the client part, not from devpanel or extension window.

Here we're splitting messages only from content script to the background script. There is no need to do that also from background script to devpanel after #580 is merged.

[zalmoxisus]

Looks like the limit is for 64 MB. To check it, add 'a'.repeat(64 * 1024 * 1024) to redux state. We'd need a test for it running from Chrome.

We'd need this also for some parts where we're sending the state back. For non-redux apps we're including the state history for importing and the state from jumped point for time travelling. For redux apps we are sending just list of actions to recompute and jumped index. Not implementing that here as we want to avoid this workaround at all.