feat(core): RDP client on IronRDP

clients::rdp connects over any caller-dialled TCP stream (direct, proxy
or SSH tunnel), upgrades to TLS and logs on with NLA (CredSSP/NTLM),
optionally falling back to TLS-only logon for servers without NLA such
as xrdp (credentials are passed so they log straight in). The server
certificate is pinned through a caller check on its SHA256 fingerprint
before any credentials are sent. The desktop decodes into the VNC
client's RGBA framebuffer; input (IronRDP's scancode/Unicode/mouse
operations), Display Control resizes and the deactivation-reactivation
sequence run on the session thread.

IronRDP's releases need three vendored patches (vendor/README.md):
picky and sspi with their RustCrypto release-candidate pins relaxed so
they share russh's stable versions (their own suites, 402 tests, pass
against them), and ironrdp-session with two unreleased upstream bitmap
fixes (#1486 stride, #1524 RDP6 orientation) without which xrdp desktops
render sheared.

Verified live against xrdp (scottyhardy/docker-remote-desktop): logon,
full desktop rendering, keyboard and mouse input.

rust/vendor/sspi/src/builders/mod.rs

@@ -0,0 +1,111 @@
+//! The builders are required to compose and execute some of the `Sspi` methods.
+
+mod accept_sec_context;
+mod acq_cred_handle;
+mod change_password;
+mod init_sec_context;
+
+use std::fmt;
+
+pub use self::accept_sec_context::{
+    AcceptSecurityContext, AcceptSecurityContextResult, EmptyAcceptSecurityContext, FilledAcceptSecurityContext,
+};
+pub use self::acq_cred_handle::{
+    AcquireCredentialsHandle, AcquireCredentialsHandleResult, EmptyAcquireCredentialsHandle,
+    FilledAcquireCredentialsHandle, WithCredentialUse, WithoutCredentialUse,
+};
+pub use self::change_password::{ChangePassword, ChangePasswordBuilder};
+pub use self::init_sec_context::{
+    EmptyInitializeSecurityContext, FilledInitializeSecurityContext, InitializeSecurityContext,
+    InitializeSecurityContextResult,
+};
+
+/// Allows to represent a value of a builder that is mandatory to be specified (during implementation
+/// of the builder).
+pub trait ToAssign: fmt::Debug {}
+/// Allows to represent a mandatory value of a builder that is already specified (during implementation
+/// of the builder).
+pub trait Assigned: ToAssign {}
+/// Allows to represent a mandatory value that is yet to be specified (during implementation
+/// of the builder).
+pub trait NotAssigned: ToAssign {}
+
+/// Simulates the presence of a value
+///
+/// Simulates the presence of the `credentials_handle` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithCredentialsHandle;
+impl ToAssign for WithCredentialsHandle {}
+impl Assigned for WithCredentialsHandle {}
+
+/// Simulates the absence of a value
+///
+/// Simulates the absence of the `credentials_handle` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithoutCredentialsHandle;
+impl ToAssign for WithoutCredentialsHandle {}
+impl NotAssigned for WithoutCredentialsHandle {}
+
+/// Simulates the presence of a value
+///
+/// Simulates the presence of the `context_requirements` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithContextRequirements;
+impl ToAssign for WithContextRequirements {}
+impl Assigned for WithContextRequirements {}
+
+/// Simulates the absence of a value
+///
+/// Simulates the absence of the `context_requirements` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithoutContextRequirements;
+impl ToAssign for WithoutContextRequirements {}
+impl NotAssigned for WithoutContextRequirements {}
+
+/// Simulates the presence of a value
+///
+/// Simulates the presence of the `target_data_representation` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithTargetDataRepresentation;
+impl ToAssign for WithTargetDataRepresentation {}
+impl Assigned for WithTargetDataRepresentation {}
+
+/// Simulates the absence of a value
+///
+/// Simulates the absence of the `target_data_representation` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithoutTargetDataRepresentation;
+impl ToAssign for WithoutTargetDataRepresentation {}
+impl NotAssigned for WithoutTargetDataRepresentation {}
+
+/// Simulates the presence of a value
+///
+/// Simulates the presence of the `output` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithOutput;
+impl ToAssign for WithOutput {}
+impl Assigned for WithOutput {}
+
+/// Simulates the absence of a value
+///
+/// Simulates the absence of the `output` value of the
+/// `AcceptSecurityContext` and
+/// `InitializeSecurityContext` builders.
+#[derive(Debug)]
+pub struct WithoutOutput;
+impl ToAssign for WithoutOutput {}
+impl NotAssigned for WithoutOutput {}