fix(cli): pass PebbleDir and SocketPath through RunOptions/ParserOptions/CmdOptions

[thp-canonical]

This builds on top of #383, and allows for a custom PebbleDir to be passed to cli.Run() in RunOptions to make sure all parts of the codebase use the passed-in values and not fall back on environment variables.

The default behavior of cli.Run(nil) stays unchanged.

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Multiple parts of the codebase currently use getEnvPaths() directly to access PEBBLE and PEBBLE_SOCKET:

• cli.Run() for the default value of client.Config.Socket (ignores PEBBLE dir)
• loadCLIState and saveCLIState in cli for the socket path (both ignore PEBBLE dir)
• runDaemon in cmd_run.go, which accesses both pebbleDir and socketPath

With #383, it is possible to pick a different socket path by passing it into cli.Run()'s options. This socket path currently only applies to Pebble client, it does not apply to the daemon part started by pebble run (because of the separate getEnvPaths() in cmd_run.go's runDaemon).

For loadCLIState and saveCLIState (both used by pebble notices and its acknowledgement command pebble okay) this PR makes sure the passed-in socket path is used (otherwise it would default to the environment variable even when a non-nil options value is passed to cli.Run()).

While "Pebble as a server" (pebble run) and "Pebble as a client" can be seen as conceptually different things, both share cli.Run as entry point.

This doesn't affect uses of getEnvPaths (and its exported name GetEnvPaths) in the unit tests.

[benhoyt]

Tests are failing on this one too. :-) It's end of day for me now, but I'll review this tomorrow.

[thp-canonical]

The PR description needs updating once the code changes are approved.