Implement trimming for attributes

[loewenheim]

1. Big attributes should be trimmed/removed before short ones. This means that we should sort attributes by ascending size and trim/remove everything after the size limit has been reached.
2. Both the attribute's key and value need to be taken into account.
3. The size limit for the attribute collection will be hardcoded initially, but will eventually need to be read from the project config.

[linear]

RELAY-177