[main] add std support

[DemesneGH]

The main branch forks from no-std and the optional std support has been added upon it. After the main branch is ready we can set it as the default branch.

The main changes are:

To add std:

• add setup_std_dependencies.sh for cloning Rust src
• add target spec for aarch64-unknown-optee and arm-unknown-optee
• optee-utee-sys and optee-utee: remove the default feature std
• examples/*/ta/Makefile: using Xargo for building when STD env is set

Building system adjustment:

• the no-std is default and the std mode can be enabled by $ export STD=y
• setup env using $ source environment: users should set ARCH_HOST (default aarch64), ARCH_TA (default aarch64) and STD (default unset) before building
• build_optee_libraries.sh builds libraries for both aarch64 and arm32
• test scripts: read the current ARCH_HOST and ARCH_TA for fetching binaries
• corresponding ci adjustment

Other updates:

• update Rust toolchain to nightly-2024-05-15
• examples/hotp/ta: fix panic

[DemesneGH]

@b49020 Could you help to review this? thanks!

[DemesneGH]

Updated for all comments. Could you please review again? Thanks! @b49020

[b49020]

PR looks fine to me for a merge now.

[DemesneGH]

merged, thanks!