Improve output and DX for sentry:test and sentry:publish commands

[stayallive]

Things fixed / improved for sentry:publish:

• Ignore commented out env variables and set new ones instead of updating a commented out variable
• Set SENTRY_TRACES_SAMPLE_RATE to 0 if transaction should be disabled and SENTRY_TRACES_SAMPLE_RATE is present in the .env
• Handle missing DSN when command is run non-interactively
• When DSN is provided with the env key in front of it, strap it away no matter the env key (just use whatever comes after the first =)
• Fix checking if .env key is set (never worked)
• Only make changes to the .env after sentry:test is a success (or no test is performed)
• Return a unix exit code depending on if the command succeeded or failed

Things fixed / improved for sentry:test:

• Use a client specific for the test command so we can be a little more in control
• Log internal SDK errors and show them as errors when sending fails
• Try and detect Let's Encrypt root related errors and show helpful hints
• If sending a event fails, don't try to send a transaction
• Only show generic "DSN is broken" message if the SDK emitted no errors
• Return a unix exit code depending on if the command succeeded or failed

And a bunch more I am probably forgetting. The inner workings have changed but the result has not and also the way they are interacted with have not changed so this should be a very transparent change and just be a glow up for some edge cases.

This should hopefully cut down on boilerplate support messages when setting up the Laravel SDK.

Fixes #521

[sforward]

The added commands will not work with Laravel 6 because of the usage of self::SUCCESS and self::FAILURE.

[stayallive]

@sforward good catch, I failed to check that, I'll replace them 👍