INavigationFilter implementations should not repeat queries

[MatteoPiovanelli-Laser]

We noticed some "repeated" queries when generating some test pages.

As the system has to build menus, if the same menu is configured in more places in the page (e.g. in more than one widget in different zones) some providers will repeat the queries they use to fetch the relevant information.
The "culprits" we found so far are:

• DefaultMenuProvider that fetches again the list of MenuParts
  

  Orchard/src/Orchard.Web/Core/Navigation/Services/DefaultMenuProvider.cs

  Line 9 in 610b3c4

  public class DefaultMenuProvider : IMenuProvider {

• TaxonomyNavigationProvider that fetches again the list of terms.
  

  Orchard/src/Orchard.Web/Modules/Orchard.Taxonomies/Navigation/TaxonomyNavigationProvider.cs

  Line 16 in 610b3c4

  public class TaxonomyNavigationProvider : INavigationFilter {

Both this situations can be fixed easily by memorizing the results of the first pass.

A PR for this is coming.

[BenedekFarkas]

Can this be solved together with #8688 or the underlying logic is too different?

[MatteoPiovanelli-Laser]

They are different/unrelated.
This one is at a "higher level", in a sense. These providers should be repeating operations they don't need.
The other issue is deeper, and I think it should be handled transparently from whatever modules are doing.

[sebastienros]

In OC these menus are cached on the page itself, using fragment caching.