Improve clarity and readability of password input documentation

Improve clarity and readability of password input documentation

Fixed #7310: Enhanced existing documentation for password input methods
- Refined descriptions for password input methods: `file:`, `fd:`, and `stdin`
- Enhanced readability and consistency in the instructions
- Clarified handling of multiple lines in read files.
- Clarified that `fd:` is not supported on Windows.

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24878)