Use bundled environment activation script file

[vinistock]

Motivation

We've been seeing 3 types of common issues in our telemetry when running the activation script - in particular for Shadowenv, but this affects all other managers except chruby and RubyInstaller:

1. Pipe encoding issues. It appears that some users have their shell's encoding configured to ASCII-8BIT, which is incompatible with the JSON we try to return and results in an unknown conversion error
2. Incompatible library for the JSON gem. Since it's a native extension, if json was compiled for a different Ruby version, we will fail to require it and thus fail to activate
3. Syntax errors. Depending on the user's shell and its configurations, we sometimes hit weird syntax errors, which happen both when requiring json and when running the script

This PR proposes a few changes to try to address these issues.

Implementation

We figured out that the first issue happens when the user sets LANG=C in their shell and has a prompt that includes certain unicode/glyph characters, which makes Ruby consider the encoding of the PS1 environment variable as ASCII-8BIT. To fix that, I started setting LANG and using the -E switch to force Ruby's encoding.

To address the other issues, my suggestion is to bundle the activation script in the extension, so that we can avoid running it with ruby -e. That helps us avoid escaping and syntax issues for different shells (e.g.: we no longer need to worry about quoting).

Additionally, I'm no longer using JSON to communicate. We essentially only need to pass key value pairs between the script and the extension, so I think we can avoid the issues coming from JSON by using a predefined separator to split them.

In this case, I'm just using a predefined string to separate values and we return/expect them in order. Note that we need a very unique separator, otherwise we risk incorrectly splitting the result.

For example, if we were to use line breaks, that would fail because you can have them in values for environment variables, which would make us incorrectly split the output.

Automated Tests

Adjusted current tests.

Manual Tests

Since I'm making changes to one of the most sensitive parts of activation, I want to cut a prerelease version for this branch to give us an opportunity to catch mistakes before stabilizing the approach.

[vinistock]

• Add debugger test with project Bundler settings #3093
• Use bundled environment activation script file #3083 👈 (View in Graphite)
• Fix file paths for exec launcher on Windows #3073
• main

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