tests: improve output information

[n0toose]

• Print to stdout as soon as the kernel successfully boots
• Print to stdout in run_simple_vm to make it clear that the kernel has been compiled
• Clarify the test-kernel being built, as the "name mismatch" between fs-test.rs and create_file.rs can be a bit confusing
• Add newline between build_hermit_bin + run_simple_vm output and output coming from the kernel
• Minor linguistic improvements

These changes may seem redundant to the trained eye (for example, it is safe to assume that the output starting with "frequency: ..." is from the kernel, thus everything that follows is from the kernel), but can be very helpful to beginners.

Based on local changes that I created for personal use, so as to better understand the debugging process.

[n0toose]

Before:

test new_file_test ... FAILED

failures:

---- new_file_test stdout ----
Building Kernel create_file
frequencies: 2604
CPU frequencies are not all equal
thread 'new_file_test' panicked at tests/common.rs:52:5:
assertion `left == right` failed
  left: 0
 right: 1
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    new_file_test

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 3.02s

After:

test new_file_test ... FAILED

failures:

---- new_file_test stdout ----
Building test kernel: create_file
Launching kernel in path: tests/test-kernels/target/x86_64-unknown-hermit/debug/create_file

frequencies: 2874
CPU frequencies are not all equal
thread 'new_file_test' panicked at tests/common.rs:55:5:
assertion `left == right` failed
  left: 0
 right: 1
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    new_file_test

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 1.97s

error: test failed, to rerun pass `--test fs-test`

[jounathaen]

Can you cherry-pick 57f01a7 into this PR?

[n0toose]

Can you cherry-pick 57f01a7 into this PR?

Recreated the commit with your author information, hope nothing broke in the process of doing so.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.38%. Comparing base (aa3379f) to head (355a3f4).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #759      +/-   ##
==========================================
- Coverage   67.65%   67.38%   -0.27%     
==========================================
  Files          18       18              
  Lines        2331     2355      +24     
==========================================
+ Hits         1577     1587      +10     
- Misses        754      768      +14     

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[n0toose]

tests: improve output information

P.S. wrote test instead of tests in the commit because of the conventional commits standard