feat:add tls support fot memcached

[ozewr]

Which issue does this PR close?

Closes #5419.

Rationale for this change

see #5419

What changes are included in this PR?

Modified the opendal::services::Memcached to support TLS connections.

Are there any user-facing changes?

Users can enable TLS using .tls() and provide the CA file using .cafile().
example:

let memcached = Memcached::default()
        .endpoint(r#"tcp://example.app.local:11211"#)
        .tls(true)
        .cafile(path);

[Xuanwo]

Would you like to add a test for memcached with tls enabled?

[ozewr]

Would you like to add a test for memcached with tls enabled?

No problem, I will complete it later.

[ozewr]

Does the Memcached service require any special configuration? During testing, I found many incorrect test results, and some tests occasionally pass while failing at other times during repeated tests. @Xuanwo
Here is my Memcached service configuration:

memcached --protocol=auto -p 11212 --enable-ssl -o ssl_chain_cert=./server.crt,ssl_key=./server.key,ssl_verify_mode=2,ssl_ca_cert=./client_ca/client_ca.crt

[Xuanwo]

Thank you for working on this and sorry for the late.

[Xuanwo]

Maybe we don't this trait?

[Xuanwo]

How about using:

pub struct Connection<IO: AsyncRead + AsyncWrite>{
    io: IO,
}

So we don't need to Box<dyn Connect> here?

[ozewr]

This might not be a good implementation.

opendal/core/src/services/memcached/backend.rs

Lines 262 to 264 in f66cf1f

	impl bb8::ManageConnection for MemcacheConnectionManager {
	type Connection = binary::Connection;
	type Error = Error;

This implementation returns a concrete type Self::Connection. If we try to use generics here, it would cause a conflict where a single function attempts to return two different types.That's because IO is a concrete type.