Auto merge of #105861 - Ayush1325:uefi-std-minimial, r=workingjubilee

Add Minimal Std implementation for UEFI

# Implemented modules:
1. alloc
2. os_str
3. env
4. math

# Related Links
Tracking Issue: rust-lang/rust#100499
API Change Proposal: rust-lang/libs-team#87

# Additional Information
This was originally part of rust-lang/rust#100316. Since that PR was becoming too unwieldy and cluttered, and with suggestion from `@dvdhrm,` I have extracted a minimal std implementation to this PR.

The example in `src/doc/rustc/src/platform-support/unknown-uefi.md` has been tested for `x86_64-unknown-uefi` and `i686-unknown-uefi` in OVMF. It would be great if someone more familiar with AARCH64 can help with testing for that target.

Signed-off-by: Ayush Singh <ayushsingh1325@gmail.com>

Author: bors