max_bid_eth not parsed .. bids could exceed cap if coinbase funded

In rbuilder.toml, the [relays.submit_config] field was not being parsed. As a result, max_bid_eth was not enforced, and if an external transfer was sent to the builder’s coinbase address while running, that amount was passed directly to the validator, effectively bypassing the relay’s bid cap.

(my fix)
To resolve this, I added max_bid_cap support inside TrueBlockValueBiddingService. Instead of per-relay limits, a single global max_bid_eth value is now parsed from the config and enforced for all relays. A cap check is applied in the build_bid function, ensuring that the bid value can never exceed the configured global limit.