feat: Add shell-style quoting and escaping to edit and run commands

feat: Add shell-style quoting and escaping to edit and run commands

Allows specifying a custom editor command with quoted spaces

`${CRATE_ROOT}` and `${GPR_FILE}` are still replaced directly, not
using parameter expansion.

The argument to `alr run -a` has been changed to use the same quoting
rules as `alr edit` instead of using the OS-specific rules provided by
`GNAT.OS_Lib.Argument_String_To_List`.

Quoting and token recognition uses the behavior for the shell command
language from the POSIX.1-2024 standard with a few changes:
- [2.2.2 Single-Quotes](https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.html#tag_19_02_02)
  - No changes
- [2.2.3 Double-Quotes](https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.html#tag_19_02_02)
  - The dollar-sign is not used for parameter expansion, command
    substitution, or arithmetic expansion
  - The backquote is not used for command substitution
  - The backslash is an escape character within double quotes only when
    immediately followed by `\` or `"`
- [2.3 Token Recognition](https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.html#tag_19_03)
  - Here-documents are not supported
  - Parameter expansion, command substitution, and arithmetic expansion
    are not supported
  - Comments are not supported
  - Alias substitution is not supported