Provide more context in BundleState docs

[onbjerg]

The docs for BundleState start with a sentence that assumes the reader has more context than they might:

revm/crates/revm/src/db/states/bundle_state.rs

Line 253 in 688c36c

/// Bundle state contain only values that got changed

It is not necessarily clear what is meant by "changed values"

Additionally, the docs mention reverts a couple of times, but never really explain what they are, so a user might be unsure of what to provide as a value for e.g. revert_range in BundleState::builder or for reverts in BundleState::new