chore: update CI toolchain and clean up code

[tabokie]

Ref #235

Update toolchain to 2022-07-13, add a makefile.

A lot of minor refactoring:

• Refactor scan_messages interface to share more code paths, and add tests for them.
• Hide LogFileFormat from outer crate, it should stay an implementation detail of file_pipe_log.
• Change DataLayout to u64, because otherwise it needs additional care to make sure Alignment(0) and NoAlignment don't coexist.
• Remove some tests that aren't very useful.

Signed-off-by: tabokie xy.tao@outlook.com

[codecov[bot]]

Codecov Report

Merging #244 (f28f309) into master (c3a6156) will increase coverage by 0.44%. The diff coverage is 99.22%.

@@            Coverage Diff             @@
##           master     #244      +/-   ##
==========================================
+ Coverage   97.24%   97.68%   +0.44%     
==========================================
  Files          30       30              
  Lines       10951    10715     -236     
==========================================
- Hits        10649    10467     -182     
+ Misses        302      248      -54     

Impacted Files	Coverage Δ
src/env/mod.rs	100.00% <ø> (ø)
src/lib.rs	100.00% <ø> (ø)
src/swappy_allocator.rs	99.23% <0.00%> (ø)
src/engine.rs	97.90% <98.23%> (+0.99%)	:arrow_up:
src/file_pipe_log/pipe.rs	99.24% <98.93%> (+0.08%)	:arrow_up:
src/config.rs	97.50% <100.00%> (ø)
src/file_pipe_log/format.rs	99.51% <100.00%> (+0.58%)	:arrow_up:
src/file_pipe_log/log_file.rs	100.00% <100.00%> (+0.43%)	:arrow_up:
src/file_pipe_log/mod.rs	98.46% <100.00%> (+0.88%)	:arrow_up:
src/file_pipe_log/pipe_builder.rs	96.20% <100.00%> (-0.04%)	:arrow_down:
... and 21 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update c3a6156...f28f309. Read the comment docs.

[tabokie]

/cc @LykxSassinator