Introduce session

[madchicken]

This PR introduces the concept of sessions when enabling the feature flag unstable-bolt-protocol-impl-v2.

The driver now provides a with_session method, allowing a session to be created on an existing connection. Sessions can be used to specify the target database, impersonate a user, and set the fetch size for queries. Bookmark handling has also been corrected to work properly within sessions.

Additionally, this PR updates the routing logic, as support for user impersonation required changes in that area.

Unfortunately, the changes are many and the PR is quite big.

Routing Refactor

Due to a deadlock caused by the use of DashMaps in the connection registry, this PR includes a complete refactor of the routing protocol. The router is now lazy and no longer relies on a separate task to fetch routing tables. This simplifies the design and improves code readability.

Graph Structure API

The PR changes the Graph structure API: the method execute_on is now forcing the user to pass the operation to perform (read or write) in order to pick the right server from the routing table.

[knutwalker]

Thanks for this PR, well done! I have some minor things around avoid allocations/clones here and there, but I would like to have at least the readme being fixed before merging

[knutwalker]

Also a note on the MSRV, there are multiple dependencies that already have a higher MSRV than 1.75. We do downgrade/pin those dependencies when generating the lockfiles for CI (

neo4rs/xtask/src/main.rs

Lines 68 to 73 in 2b571c4

	("idna_adapter".to_owned(), "1.2.0"),
	("litemap".to_owned(), "0.7.4"),
	("home".to_owned(), "0.5.9"),
	("testcontainers".to_owned(), "0.23.1"),
	("testcontainers-modules".to_owned(), "0.11.4"),
	("zerofrom".to_owned(), "0.1.5"),

and

neo4rs/xtask/src/main.rs

Lines 100 to 106 in 2b571c4

	("idna_adapter".to_owned(), "1.2.0"),
	("litemap".to_owned(), "0.7.4"),
	("home".to_owned(), "0.5.9"),
	("serde_repr".to_owned(), "0.1.5"),
	("testcontainers".to_owned(), "0.23.1"),
	("testcontainers-modules".to_owned(), "0.11.4"),
	("zerofrom".to_owned(), "0.1.5"),

-- those two lists might even be different at times). It also means that a user can't just add neo4rs on the MSRV version without also having to downgrade on their end (which they would have to do anyway).
We still have the latest (or reasonably latest) versions in the dependencies, so that you don't have to use older versions and recent rust versions.

I have a preference to "pin" time to 0.3.41 in the xtask script over raising the MSRV.

[knutwalker]

actually, I did the changes in #265 -- you should be able to keep 1.75 after rebasing

[knutwalker]

👍 thanks!