- Filters env vars specific to agent-exec from the exec'd process. This
is to prevent any issues when developing Coder in Coder, particularly
agent tests in the cli pkg.
- Fixes an issue where oom scores would fail to be adjusted in cases
where the `coder` binary has capabilities set on it. This is because
`PR_SET_DUMPABLE` is set to `0` when a process is executed with elevated
capabilities. The fix is to flip `PR_SET_DUMPABLE` to `1` prior to
writing to `oom_score_adj`.
- Integrates the `agentexec` pkg into the agent and removes the
legacy system of iterating over the process tree. It adds some linting
rules to hopefully catch future improper uses of `exec.Command` in the package.
