feat: drop read_only on a connection returned back to a pool

[IlyaFaer]

Current connections reset mechanism doesn't drop read_only property of a connection returned back to a connections pool. It makes the following cases possible:

• user initiates a ReadOnly connection, executes some operations and returnes the connection back to the pool (automatically)
• user initiates the next connection, without making it ReadOnly, but the pool returns the connection, which was toggled to the ReadOnly mode earlier (as it's a pool, it returns the connections created earlier, it is its purpos).

Such a situation can be very unexpected and will require for user to write additional logic to understand if the connection can be used in their case. To avoid it, we better drop read_only attribute to its default value when a connection is returned back to pool.

P.S. because of the same reasons we're already dropping staleness attribute on a connection reset.

[vi3k6i5]

LGTM