Check if a signed URL is specified and use it download tools

[MatteoPologruto]

Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• Tests for the changes have been added (for bug fixes / features)

• What kind of change does this PR introduce?

Code enhancement

• What is the current behavior?

There are two ways of dowloading tools: Download and Install. The first one downloads and installs the tools from the package index only, while it is possible to provide a signed URL and a checksum to the second one to download a tool from there.

• What is the new behavior?

Download is wrapped inside DownloadFromURL to align it to Install.

• Does this PR introduce a breaking change?

No

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.05128% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 20.10%. Comparing base (2fa738f) to head (afe92ea).
Report is 4 commits behind head on main.

Files	Patch %	Lines
v2/pkgs/tools.go	78.57%	6 Missing ⚠️
tools/download.go	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #953      +/-   ##
==========================================
- Coverage   20.64%   20.10%   -0.55%     
==========================================
  Files          42       42              
  Lines        2601     2537      -64     
==========================================
- Hits          537      510      -27     
+ Misses       1967     1943      -24     
+ Partials       97       84      -13     

Flag	Coverage Δ
unit	20.10% <82.05%> (-0.55%)	⬇️

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