Drop a few more uses of Task

[cgwalters]

It wasn't a useful abstraction in the end for most cases.

[gemini-code-assist]

Code Review

This pull request successfully removes the custom Task abstraction, replacing it with direct usage of std::process::Command and helper extension traits from bootc_utils::CommandRunExt. This is a positive change that simplifies the codebase. The new implementation generally improves error reporting by capturing stderr on command failures. I've identified one minor regression where an error context attribute was removed, which I've suggested restoring to maintain detailed error diagnostics. Otherwise, the changes are excellent.

[gemini-code-assist]

The #[context("Failed to wipe {dev}")] attribute was removed. This attribute provides valuable context to error messages when the wipefs command fails. Without it, the error message will be less specific, making debugging harder. It would be beneficial to restore this attribute to improve error diagnostics.

Suggested change

	pub(crate) fn wipefs(dev: &Utf8Path) -> Result<()> {
	#[context("Failed to wipe {dev}")]
	pub(crate) fn wipefs(dev: &Utf8Path) -> Result<()> {