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-commenter]

Codecov Report

Merging #44 (92e400e) into master (00012a7) will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #44      +/-   ##
==========================================
+ Coverage   89.74%   89.80%   +0.05%     
==========================================
  Files          36       36              
  Lines        1795     1795              
==========================================
+ Hits         1611     1612       +1     
+ Misses        184      183       -1     

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

... and 1 file with indirect coverage changes

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[jbytecode]

@timholy - many thanks!