Standardise assertions for remote HTTP tests

[johnbillion]

The order of assertions for remote HTTP request tests aren't entirely consistent, which can be a problem when an HTTP request fails and you see a test-specific assertion failure instead of information about why the request failed.

For every HTTP request test where the request is expected to succeed, the order should be:

1. skipTestOnTimeout() so timeouts don't cause the test to fail
2. assertNotWPError() so if the request results in an error then the full WP_Error message gets output
3. HTTP status code assertions, if necessary
4. All other assertions

[johnbillion]

In 58108:

Build/Test Tools: Standardise the assertions for remote HTTP request tests.

This ensures that as much information as possible is shown when an HTTP request fails during an external HTTP test.

Fixes #61148

https://core.trac.wordpress.org/changeset/58108