[cleanup] Refactor Eldritch Runtime

[KCarretto]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Updates eldritch::Runtime to manage it's own thread, since callers were being forced to call it in a separate thread anyways. Now we support an eldritch::start API for running tomes in a separate thread, which returns a Runtime. The Broker has been removed, and now Runtime is the callers interface to interact with the running eldritch thread. We have also renamed the eldritch::Client to eldritch::Environment, which is still intended to be used by eldritch functions to interface with the caller (request files, report processes, etc.)

Example Usage

let mut runtime = eldritch::start(eldritch::pb::Tome{...});

// The tome is now executing, we can begin checking for output
let _output = runtime.collect_text();

// ...

// Wait for the tome to finish
runtime.finish().await;

[Cictrone]

lgtm

[codecov]

Codecov Report

Attention: 53 lines in your changes are missing coverage. Please review.

Comparison is base (05a2be7) 70.88% compared to head (b6d1577) 70.78%.

Files	Patch %	Lines
implants/lib/eldritch/src/runtime/exec.rs	77.31%	22 Missing ⚠️
implants/imix/src/task.rs	0.00%	9 Missing ⚠️
implants/imix/src/install.rs	0.00%	7 Missing ⚠️
implants/lib/eldritch/src/runtime/drain.rs	66.66%	7 Missing ⚠️
implants/imix/src/agent.rs	0.00%	2 Missing ⚠️
implants/lib/eldritch/src/assets/copy_impl.rs	88.88%	2 Missing ⚠️
implants/lib/eldritch/src/runtime/environment.rs	84.61%	2 Missing ⚠️
implants/golem/src/main.rs	91.66%	1 Missing ⚠️
implants/lib/eldritch/src/runtime/mod.rs	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #577      +/-   ##
==========================================
- Coverage   70.88%   70.78%   -0.10%     
==========================================
  Files         141      141              
  Lines       10225    10184      -41     
==========================================
- Hits         7248     7209      -39     
+ Misses       2811     2809       -2     
  Partials      166      166              

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