Collect the number of bundles and transactions the builder puts in a block

[come-maiz]

To bootstrap data collection from our builder, I propose we collect these two numbers:

How many bundles are included in a block
How many transactions come from the mempool

[come-maiz]

There will be more builders, so how do we collect this information from them?

Do we ask them to provide some metadata along with the block?
Do we ask them to provide a data API to consult?
Do we trust them?
Should we do the calculations ourselves by looking at the data collected from our relay?