Adjusts the `gpg-agent.conf` template as follows:
1. Adds more `pinentry-program` variants likely to be found on current
Linux and macOS systems.
2. Groups entries by OS and package.
3. Makes all `pinentry-program` directives inactive (commented-out).
At present, the `pinentry-program` directive active by default is:
```
pinentry-program /usr/bin/pinentry-curses
```
This works on Linux but fails on macOS.
However, if `gpg-agent.conf` either does not exist, or exists but does
not contain **any** active `pinentry-program` directives, then my
experimentation shows current OS releases behave as follows:
* Linux invokes:
- `/usr/bin/pinentry-gnome3` (if a Desktop environment is available)
- `/usr/bin/pinentry-curses` (otherwise)
I have tested Debian, Ubuntu and Raspberry Pi OS.
* macOS invokes:
- `/usr/local/bin/pinentry-curses` (Intel)
- `/opt/homebrew/bin/pinentry-curses` (Apple)
Those are true when `gnupg` has been installed by HomeBrew. I can't
test either MacPorts or MacGPG2 directly but research suggests:
- `/opt/local/bin/pinentry` (MacPorts)
- `/usr/local/MacGPG2/libexec/pinentry-mac.app/Contents/MacOS/pinentry-mac` (MacGPG2)
Signed-off-by: Phill Kelley <34226495+Paraphraser@users.noreply.github.com>
