perf: early validate all messages before encoding

[muktihari]

Validating messages early give several advantages:

1. If invalid message occurs, we can return early without doing unnecessary works such as marshaling, calculate CRC or even do a syscall to write to the file.
2. If normal writer is given (a writer without offset writer capability), the encoding speed is improved by geomean 16% since we don't need to validate messages twices. Benchmark:

goos: linuxl goarch: amd64l pkg: benchfitl cpu: Intel(R) Core(TM) i5-5257U CPU @ 2.70GHz
                           │   old.txt   │               new.txt               │
                           │   sec/op    │   sec/op     vs base                │
Encode/muktihari/fit_raw-4   93.57m ± 8%   74.63m ± 3%  -20.24% (p=0.000 n=10)
Encode/muktihari/fit-4       157.2m ± 7%   136.7m ± 2%  -13.01% (p=0.000 n=10)
geomean                      121.3m        101.0m       -16.71%

3. We can release all objects generated by the message validator early, so it can be garbage-collected as soon as we are done validating. The objects are only be generated when it encounters developer data.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.94%. Comparing base (e3d3e16) to head (27b5306).
Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##            master     #454      +/-   ##
===========================================
- Coverage   100.00%   99.94%   -0.06%     
===========================================
  Files           42       42              
  Lines         3659     3687      +28     
===========================================
+ Hits          3659     3685      +26     
- Misses           0        2       +2     

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