Add upload frequency param in config

[louiszawadzki]

What does this PR do?

Adds an uploadFrequency parameter to change the upload frequency of batches of data.

Additional Notes

Demo:

iOS

Rare (50 secs between uploads):

Frequent (5 secs between uploads):

Android (clicking on a button every second to give an idea of time between uploads)

Rare:

Frequent:

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