Auto merge of #116207 - Ayush1325:uefi_stdio, r=Mark-Simulacrum

Stdio support for UEFI

- Uses Simple Text Output Protocol and Simple Text Input Protocol
- Reading is done one character at a time
- Writing is done with max 4096 characters

# Quirks
## Output Newline
- UEFI uses CRLF for newline. So when running the application in UEFI shell (qemu VGA), the output of `println` looks weird.
- However, since the UEFI shell supports piping output, I am unsure if doing any output post-processing is a good idea. UEFI shell `cat` command seems to work fine with just LF.

## Input Newline
- `Stdin.read_line()` method is broken in UEFI shell. Pressing enter seems to be read as CR, which means LF is never encountered.
- Works fine with input redirection from file.

CC `@dvdhrm`

Author: bors