Migrate from SnoopPrecompile to PrecompileTools

[timholy]

This pull request migrates the package from SnoopPrecompile to PrecompileTools.
PrecompileTools is nearly a drop-in replacement except that there are changes in naming and how developers locally disable precompilation (to make their development workflow more efficient). These changes are described in PrecompileTool's enhanced documentation, which also includes instructions for users on how to set up custom "Startup" packages, handling precompilation tasks that are not amenable to workloads, and tips for troubleshooting.

Why the new package? It meets several goals:

• The name "SnoopPrecompile" was easily confused with "SnoopCompile," a package designed for analyzing rather than enacting precompilation.
• SnoopPrecompile/PrecompileTools has become (directly or indirectly) a dependency for much of the Julia ecosystem, a trend that seems likely to grow with time. It makes sense to host it in a more central location than one developer's personal account.
• As Julia's own stdlibs migrate to become independently updateable (true for DelimitedFiles in Julia 1.9, with others anticipated for Julia 1.10), several of them would like to use PrecompileTools for high-quality precompilation. That requires making PrecompileTools its own "upgradable stdlib."
• We wanted to change the use of Preferences to make packages more independent of one another. Since this would have been a breaking change, it seemed like a good opportunity to fix other issues, too.

For more information and discussion, see this discourse post.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (e34e56f) 100.00% compared to head (780c6aa) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #58   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          154       154           
=========================================
  Hits           154       154           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/workload.jl	100.00% <ø> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.