Remote Keystore based on OPTEE

[ghost]

This PR adds support to the substrate node for a secret management solution using OPTEE that holds the secrets for the node in an HSM separate from the machine running the node.

Please contact us here or via email at hello@zondax.ch (or other established channels where available) for any clarification.

---

There are currently 2 blockers with merging/rebasing with master:

• Rust version requirement
  The hsm image is pinned with Rust 1.54 (which doesn't understand 2021 edition)
• Unreleased crates (new versions)
  The project relies on a few crates from the substrate primitives and core, such as sp-keystore, most to conform to the traits required for a keystore, but as the development branches make use of unreleased crates based on path dependencies, it becomes difficult to patch these due to how cargo handles dependency resolution (basically it first attempts to look for the crate version specified on the manifest, and if not found it errors, without resolving to patches) (for a recently merged branch see teekeystore-merged

/cc @jleni @neithanmo

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User @becominginsane, please sign the CLA here.

[ghost]

Notice hasn't been removed because we lack the labels and we are not able to add them (or at least not me)

[stale]

Hey, is anyone still working on this? Due to the inactivity this issue has been automatically marked as stale. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

Hey, is anyone still working on this? Due to the inactivity this issue has been automatically marked as stale. It will be closed if no further activity occurs. Thank you for your contributions.