Add unit tests for HTTP commands. (#8267)

# Description

Following the comment from @fdncred:
https://github.com/nushell/nushell/pull/8144#issuecomment-1442514338. I
added some unit tests for HTTP commands. The tests are not exhaustive,
but at least, this is a first good step IMO.

# User-Facing Changes

None.

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-command/tests/commands/network/http/mod.rs

@@ -0,0 +1,6 @@
+mod delete;
+mod get;
+mod head;
+mod patch;
+mod post;
+mod put;