tests: replace the flat list of contexts with a hash

Dependencies

• [2] 3G475GRT Split out dependent tests in to its own .t
• [3] 3AKZKWCR RunCommand: Test
• [4] UIA3ULNU Give each test its own Nix directories
• [5] E4TV6NH6 RunCommand: pass homepage, description, license, system, and nixname
• [6] HX4QYOYA add first evaluations tests
• [7] HENEI752 evaluate-dependent-jobsets: clean up test to be more clear
• [8] OWRS526H Create an ephemeral PostgreSQL database per test
• [9] 5SMQ2PLK Fix tests

Change contents

• replacement in tests/build-products.t at line 5
  [4.946]→[4.1197:1237](∅→∅)
  − (my $datadir, my $pgsql) = test_init();
  [4.946]

  [4.474]
  + my %ctx = test_init();
• replacement in tests/evaluate-basic.t at line 6
  [4.66]→[4.66:106](∅→∅)
  − (my $datadir, my $pgsql) = test_init();
  [4.66]

  [4.106]
  + my %ctx = test_init();
• replacement in tests/evaluate-dependent-jobsets.t at line 5
  [2.35]→[2.35:75](∅→∅)
  − (my $datadir, my $pgsql) = test_init();
  [2.35]

  [2.75]
  + my %ctx = test_init();
• replacement in tests/lib/Setup.pm at line 65
  [4.896]→[4.2197:2224](∅→∅)
  − return ($dir, $pgsql);
  [4.896]

  [4.915]
  + return (

  + tmpdir => $dir,

  + db => $pgsql

  + );
• replacement in tests/plugins/runcommand.t at line 8
  [3.1319]→[3.1319:1357](∅→∅)
  − (my $datadir, my $pgsql) = test_init(
  [3.1319]

  [3.1357]
  + my %ctx = test_init(