Improves build time by 30%, resolving issue 5123 "Charts Framework takes a long time to build"

[drewster99]

Resolves issue #5123 "Charts framework takes a long time to build" (https://github.com/danielgindi/Charts/issues/5123) by implementing the recommendations listed at the end of the issue. These changes improved the clean full Debug build time by 30%.

Issue Link :link:

Charts framework takes a long time to build

Goals :soccer:

Improves build times of the Charts framework target for both clean and incremental Debug builds, enabling more parallelization during building.

Implementation Details :construction:

This PR makes the following changes:

• Sets Eager Linking build setting to Yes for Charts framework target
• Sets Enable Module Verifier build setting to No for Debug builds
• Sets Compilation Mode to Incremental for Debug builds
• Added -Xfrontend -warn-long-expression-type-checking=50 (or perhaps use 100) to OTHER_SWIFT_FLAGS so the Swift compiler will emit warnings for expressions that take a long time to type-check. The number after the = is the number of milliseconds threshold, above which warnings will be emitted.
• Refactored the slow type-checking hotspots identified above in ChartAnimationEasing.swift, breaking out expressions which are slow to type-check into separate, quicker-to-type-check expressions.

Testing Details :mag:

To test/verify the build time improvement, use these simple steps -- first with the existing code, and then again using this PR branch/commit:

• Quit Xcode
• Delete DerivedData (rm -rf $HOME/Library/Developer/Xcode/DerivedData)
• Open Xcode
• Open Charts.xcworkspace
• Hit Command-B to make a debug build
• Look at the total time at the end of your build log