feat: print type when empty; add fundamental type

[youthlin]

• errors.New and errors.Errorf(when args not contains error type) now returns *errors.fundamental
• when a wrap error do not add any additional message, then print it's type in detail mode

type Err struct {
	err error
	foo string
}

func newErr(err error) error { return &Err{err: err, foo: "foo"} }
func (e *Err) Error() string { return e.err.Error() }
func (e *Err) Unwrap() error { return e.err }

func TestEmpty(t *testing.T) {
	err := errors.Errorf("newErr") // Line 50
	err = newErr(err)
	fmt.Printf("err=%+v\n", errors.Wrapf(err, "prefix")) // Line 52
}

Output:
// note the (3) and (4) error

err=prefix: newErr
(1) attached stack trace
 │ -- stack trace:
 │ code.gopub.tech/errors_test.TestEmpty
 │ 	/go/src/code.gopub.tech/errors/format_test.go:52
 │ [...repeated from below...]
Next: (2) prefix
Next: (3) *errors_test.Err
Next: (4) newErr
 │  -- stack trace:
 │  code.gopub.tech/errors_test.TestEmpty
 │  	/go/src/code.gopub.tech/errors/format_test.go:50
 │  testing.tRunner
 │  	/sdk/go1.21.6/src/testing/testing.go:1595
 │  runtime.goexit
 └─ 	/sdk/go1.21.6/src/runtime/asm_amd64.s:1650
Error types: (1) *errors.withStack (2) *errors.withPrefix (3) *errors_test.Err (4) *errors.fundamental

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (430e6a0) 61.01% compared to head (1c53ea8) 62.55%.

Files	Patch %	Lines
format.go	63.63%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #4      +/-   ##
==========================================
+ Coverage   61.01%   62.55%   +1.54%     
==========================================
  Files          12       13       +1     
  Lines        1126     1151      +25     
==========================================
+ Hits          687      720      +33     
+ Misses        407      398       -9     
- Partials       32       33       +1     

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