[Malleability Immutable] Removed non-constructor mutations for Attestation, ResultApprovalBody and ResultApproval structs

[AndriiDiachuk]

closes: #7298 #7299 #7300

Context

In this PR were added constructor for Attestation, ResultApprovalBody and ResultApproval structs and removed non-constructor mutations for those structs.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 48.71795% with 20 lines in your changes missing coverage. Please review.

Project coverage is 41.13%. Comparing base (e41c00c) to head (ce3785d).

Files with missing lines	Patch %	Lines
model/flow/resultApproval.go	0.00%	18 Missing ⚠️
network/codec/codes.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7417      +/-   ##
==========================================
- Coverage   41.15%   41.13%   -0.02%     
==========================================
  Files        2210     2210              
  Lines      193935   193953      +18     
==========================================
- Hits        79808    79781      -27     
- Misses     107520   107566      +46     
+ Partials     6607     6606       -1     

Flag	Coverage Δ
unittests	41.13% <48.71%> (-0.02%)	⬇️

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[tim-barry]

One main comment related to data structures originating from the network, where I think the structure should be considered "finished construction" (for purposes of immutability and ID caching) after deserialization:

flow-go/network/codec/cbor/codec.go

Lines 102 to 109 in 0075514

	msgInterface, what, err := codec.InterfaceFromMessageCode(msgCode)
	if err != nil {
	return nil, err
	}
	// unmarshal the payload
	//bs2 := binstat.EnterTimeVal(fmt.Sprintf("%s%s%s:%d", binstat.BinNet, ":wire>4(cbor)", what, code), int64(len(data))) // e.g. ~3net:wire>4(cbor)CodeEntityRequest:23
	err = cborcodec.DefaultDecMode.Unmarshal(data[1:], msgInterface) // all but first byte