Allow specifying stubs as a dependency, not a path

[Calvin-L]

Today the way you configure stubs is with the -Astubs=... option, which takes a filesystem path:

configure<CheckerFrameworkExtension> {
    extraJavacArgs = listOf(
        "-Astubs=${project.rootProject.rootDir}/stubs",
    )
}

It would be nicer to specify a subproject or dependency containing stub files instead. This has many benefits:

• Simpler setup for giant multi-repo projects (today this has to be done by adding a git-clone-shared-components step to the build so we can have a filesystem path instead of a dependency coordinate---very ugly and difficult to get right!)
• This would (hopefully) fix Checker stubs are likely NOT considered an input to Java compilation #135
• This would (hopefully) fix The -Astubs parameter can't contain a relative path which impacts Gradle task cacheability #252
• Extending this idea with testCheckerFrameworkStubs(...) would fit the need in Need to configure an additional .astub file for "test" and/or "testFixtures" #223

Example:

dependencies {
    checkerFrameworkStubs(project(":localStubs")) // stubs from local subproject
    checkerFrameworkStubs("mygroup:shared-stubs:1.0.0") // stubs from some common repo
    testCheckerFrameworkStubs(project(":testStubs")) // stubs for test libraries
}

(This ask is essentially the same as typetools/checker-framework#4058 and typetools/checker-framework#6813.)