Recursively scan Perl code for dependencies

Changes for 1.32 - 2023-07-05

• Ensure $inc gets removed from the start of $File::Find::name
• Provide dedicated test scripts for some tests instead of using the test scripts themselves: Test::More draws in all kinds of stuff, totally unpredictable
• Rewrite test helpers in t/Utils.pm to use Test::More's subtest feature
• Code cleanup; fix detection of 'do STRING' (cf PR #15)
• scandeps.pl: sort items in "used by" column
• Handle spaces after quote operator, e.g. eval qq {Some::Module}
• Fixes #12: share dir not returned when require module is in an eval
• Recognize constructs like "eval qq{require Inline::C}".
• Recognize idioms like "if (eval { require Foo }) { ..."
• Add %preload rules for some Mojo resource files
• Bump perl dependency to guard against ancient perls without FindBin::again()
• Add tool to trace when (and from where) Perl searches for a module