DTLS flights re-sending delay is incorrect

[Shaienn]

Describe the bug
DTLS flights re-sending delay is incorrect. DTLS doubles flight retransmission timer value each time when DTLS state machine entering next state despite there is no retransmission occurred.

To Reproduce
Some flight (except the first one) content should be lost after sending (UDP packet lost). Then it need to wait until the lost flight content will be re-sent and measure the time between first and second sending. Measured time will be greater than 1 second. On flight4 it can be 8 seconds.

Expected behavior
According to RFC I expect that timer value will not be increased without retransmission.

https://datatracker.ietf.org/doc/html/rfc9147#section-5.8.1-7.1

The retransmit timer expires: the implementation transitions to the SENDING state, where it retransmits the flight, adjusts and re-arms the retransmit timer

https://datatracker.ietf.org/doc/html/rfc9147#section-5.8.2-2

...implementations SHOULD use an initial timer value of 1000 ms and double the value at each retransmission...

https://datatracker.ietf.org/doc/html/rfc9147#section-5.8.2-5

Implementations SHOULD retain the current timer value until a message is transmitted and acknowledged without having to be retransmitted

Affected versions
Erlang/OTP 26.

Additional context

There is some code which changes DTLS statem states and shows that retransmit value is increased after each state transition.

-module(test).
-include_lib("ssl/src/ssl_connection.hrl").
-compile(export_all).

close(_) -> ok.

start() ->
 application:start(crypto),
 application:start(asn1),
 application:start(public_key),
 application:start(ssl),
 Role = client,
 SslOpts0 = [{protocol, dtls}, {cb_info, {?MODULE,udp,udp_closed,udp_error,udp_passive}},
   {handshake, hello}, {verify_peer, none}],
 {ok, SslConfig} = ssl:handle_options(SslOpts0, Role, dummy),
 #config{ssl = SslOpts, transport_info = CbInfo} = SslConfig,

 DtlsStatem = proc_lib:spawn_link(dtls_connection, init, [[Role, host, port, {{peer, port}, #{role => Role}}, {SslOpts, #socket_options{}, []}, user, CbInfo]]),
 {initial_hello, #state{protocol_specific = #{flight_state := {retransmit, 1000}}} = State1} = sys:get_state(DtlsStatem),
 exit(DtlsStatem, normal),

 {keep_state, State2, _} = dtls_connection:hello(enter, dummy, State1),
 #state{protocol_specific = #{flight_state := {retransmit, 2000}}} = State2,

 {keep_state, State3, _} = dtls_connection:hello(enter, dummy, State2),
 #state{protocol_specific = #{flight_state := {retransmit, 4000}}} = State3,

 {keep_state, State4, _} = dtls_connection:certify(enter, dummy, State3),
 #state{protocol_specific = #{flight_state := {retransmit, 8000}}} = State4,

 {keep_state, State5, _} = dtls_connection:cipher(enter, dummy, State4),
 #state{protocol_specific = #{flight_state := {retransmit, 16000}}} = State5,

 ok.

I have created pull request for the issue: #7300

[IngelaAndin]

OTP-26.0.1 has been released