Traverse the filesystem only once when looking for UDI and Subiquity snaps.

[CarlosNihelton]

Here is the key of this PR:

        // if none of the required snaps exist in the rootfs no UI will be available.
-        if (!internal::hasUdiSnap() && !internal::hasSubiquitySnap()) {
+        if (!internal::hasAnyOfSnaps(L"ubuntu-desktop-installer"sv, L"subiquity"sv)) {

For that to be possible, hasAnyOfSnaps() has to be implemented as a template function that can accept a variadic number of string_view arguments and applies the existing algorithms to find entries inside the snap directory matching one of the supplied arguments. Since that receives a variadic argument in order to nicely compose find_file_if and std::any_of we put together a push_back_many algorithm that populates a vector of string_views from a variadic argument list.

BTW, find_file_if returns a bool instead of iterator, so more like std::any_of than std::find_if, thus the function was renamed to any_file_of.

And since there were some documentation comments lacking on the algorithms.h header and some unevitable linter complains about parameters of the same type in starts/ends_with algorithms, I put some comments to stop linter at those lines.

I think it is easier to review this PR commit by commit.

[github-actions]

⚠️ Please check out carefully the isses found by clang-tidy in the new code ⚠️
⚠️ clang-format found formatting issues in the code submitted.:warning:
Make sure to run clang-format and update this pull request.
(1/1)

[EduardGomezEscandell]

Minor performance comment