Add support for the Spice programming language.
Spice (`spicelang`) is a simple, AOT compiled, LLVM-based systems
language with focus on practicality and performance.
**Key features of Spice**
- simplicity - see what you get aproach with batteries included
- performance: As Spice uses LLVM as its primary backbone, it competes
with the performance of other LLVM-based compilers
- enhanced safety: Spice implements an enhanced safety mechanism, which
includes builtin heap type with auto-free and more
- cross-compile support: Currently x86_64, AArch64 and wasm32 are
supported cross-compilation targets, but more to come
- Pretty good C and C++ interop
**Links**
- Source code: https://github.com/spicelang/spice
- Website: https://spicelang.com
- Playground (own CE instance): https://play.spicelang.com
- Infra PR: https://github.com/compiler-explorer/infra/pull/1229
**Things this PR addresses**
- General support for Spice
- Three code examples
- Spice mode (Syntax highlighting)
- Opt pipeline support
- LLVM mca and osaca support
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