fix(proto): implement fmt.Formatter for Field and Value

[muktihari]

There are two objectives that this PR solves by implementing fmt.Formatter for proto.Field and proto.Value.

1. Reduce gotcha when printing proto.Value, as proto.Value has the same implementation of fmt.Stringer, but we treat it as a special case method to retrive string value, rather than the underlying value formatted as a string. Example:

   val := proto.Uint8(10)
   fmt.Println(val)       // We might expect 10, but it prints "" since it's not a string
   fmt.Println(val.Any()) // Previous workaround, we must call Any() method

   And thing gets trickier when we print a type containing proto.Value such as proto.Field or maybe if we print the whole proto.FIT itself, as it will trigger fmt to call (proto.Value) String() string method. Related issue: Totals not complete, most of the unknown fields are missing #520

   Now we can just do:

   val := proto.Uint8(10)
   fmt.Println(val)
   // Output:
   // 10

2. Enable more verbose printing format for proto.Field for debugging purposes. Since proto.FieldBase is embedded in proto.Field as a pointer, fmt prints the pointer address to proto.FieldBase instead of its value. In general, we need to know the description of the field such as field number, field name, type etc when printing proto.Field. Now, we have it:

   field := factory.CreateField(mesgnum.Record, fieldnum.RecordDistance).WithValue(uint32(7))
   
   fmt.Println(field)
   // Output:
   // old: {0x59ee20 7 false}
   // new: {(0x59ee20)(&{distance 5 uint32 uint32 false true 100 0 m [] []}) 7 false}
   
   fmt.Printf("%+v\n", field)
   // Output:
   // old: {FieldBase:0x59ee20 Value:7 IsExpandedField:false}
   // new: {FieldBase:(0x59ee20)(&{Name:distance Num:5 Type:uint32 BaseType:uint32 Array:false Accumulate:true Scale:100 Offset:0 Units:m Components:[] SubFields:[]}) Value:7 IsExpandedField:false}

   We keep the pointer address in the formatted string in case it matters.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (5515a76) to head (8746aa9).
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #521   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           42        42           
  Lines         4618      4641   +23     
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+ Hits          4618      4641   +23     

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