rustc_target: Sync with stdarch (important parts)

[a4lg]

Of RISC-V features defined in stdarch, this commit adds ratified extensions satisfying following criteria:

• Formerly a part of the I extension and splitted thereafter (now ratified as I + Zifencei + Zicsr + Zicntr + Zihpm) or
• Dicoverable from newer versions of the Linux kernel (Ztso and Zihintpause).

This is based on the latest ratified ISA Manuals (version 20240411).

LLVM Definitions:

• Zifencei
• Zicsr
• Zicntr
• Zihpm
• Ztso
• Zihintpause

One of those, Zicsr, is a dependency of many other ISA extensions and this commit adds correct dependencies to Zicsr except V (due to ongoing PR #138742).

---

Related:

• Tracking issue for RFC 2045: improving #[target_feature] #44839
  (riscv_target_feature)
• Tracking Issue for RISC-V Ratified Extensions Intrinsics #114544
  (This PR can be a prerequisite of resolving a part of that tracking issue)
• rustc_target: Add more RISC-V vector-related features and use zvl*b target features in vector ABI check #138742
  (Touches the same place and vector extensions depend on Zicsr)

NOT Related but linked:

• Some -Ctarget-features must be restrained on RISCV #132618
  (This PR won't be blocked by this issue since none of those extensions do not change the ABI)

@rustbot label +T-compiler +O-riscv +A-target-feature

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[a4lg]

@rustbot r? @Amanieu

[a4lg]

Hmm, considering the minimum LLVM version, I have to remove Ztso for now (LLVM 19 stabilized support for Ztso).