Better naming for constructor funcs

[farazdagi]

What type of PR is this?

Other / Better naming for initializing funcs

What does this PR do? Why is it needed?

• A package name and its contents' names are coupled, since client code uses them together. Therefore, conventionally, we prefer the following:
  • initsync.NewService() instead of initsync.NewInitSyncService() (both to avoid stuttering and because when some constructor returns type T, if type doesn't coincide with package name it is conventional to name it NewT(), not NewSomePartOfPackageNameT()). For the most of our services, we do indeed have service.NewService() - for those diverging, this PR provides a fix.
  • When package name and returned type do indeed coincide, the conventional naming is just New(). That's instead of wallet.NewWallet() (for function that returns *Wallet i.e. name of returned type and package coincide), we'd prefer wallet.New() (and expect it return Wallet or `*Wallet). This PR fixes number of such occurrences.

Which issues(s) does this PR fix?

N/A

Other notes for review

• For more info, please, see https://blog.golang.org/package-names

[codecov]

Codecov Report

Merging #7316 into master will decrease coverage by 0.10%.
The diff coverage is 78.94%.

@@            Coverage Diff             @@
##           master    #7316      +/-   ##
==========================================
- Coverage   60.02%   59.92%   -0.11%     
==========================================
  Files         416      416              
  Lines       29950    29857      -93     
==========================================
- Hits        17978    17891      -87     
- Misses       9032     9038       +6     
+ Partials     2940     2928      -12