Improve tx type count observability in pool

[mattsse]

trafficstars

Describe the feature

currently we're only tracking txs by pool, which means that these metrics only track non pending blob txs:

https://github.com/paradigmxyz/reth/blob/098018db493c48e8bc9e4a4fc4d62e2b668de724/crates/transaction-pool/src/metrics.rs#L34-L37

https://github.com/paradigmxyz/reth/blob/098018db493c48e8bc9e4a4fc4d62e2b668de724/crates/transaction-pool/src/pool/blob.rs#L12-L12

hence these metrics aren't useful to monitor how many blob transactions are currently in the entire txpool.

we would like this for all transaction types

TODO

• introduce new metrics for legacy,eip2930,1559,4844 count

we can either try tracking this on a per tx operation basis or by checking the total list by doing a fold over all transactions in the pool, which is more expensive. https://github.com/paradigmxyz/reth/blob/098018db493c48e8bc9e4a4fc4d62e2b668de724/crates/transaction-pool/src/pool/txpool.rs#L930-L931

tracking all tx ops is more complex, so imo we're okay with updating these metrics when we update the pool for now this should be accurate enough:

https://github.com/paradigmxyz/reth/blob/098018db493c48e8bc9e4a4fc4d62e2b668de724/crates/transaction-pool/src/pool/txpool.rs#L432-L432

Additional context

No response