Support nullish coalescing with tree-shaking

[lukastaegert]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:
Resolves #3544

Description

This adds nullish coalescing support including advanced tree-shaking support for these expressions. At that point, the only thing we are missing is optional chaining, let's keep our fingers crossed!

Tree-shaking examples via the REPL

[rollup-bot]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#nullish-coalescing

or load it into the REPL:
https://rollupjs.org/repl/?circleci=10915

[codecov]

Codecov Report

Merging #3548 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3548   +/-   ##
=======================================
  Coverage   96.24%   96.25%           
=======================================
  Files         176      176           
  Lines        6025     6027    +2     
  Branches     1777     1778    +1     
=======================================
+ Hits         5799     5801    +2     
  Misses        112      112           
  Partials      114      114           

Impacted Files	Coverage Δ
src/ast/nodes/ExportAllDeclaration.ts	100.00% <ø> (ø)
src/ast/nodes/ExportNamedDeclaration.ts	100.00% <ø> (ø)
src/ast/nodes/NodeType.ts	100.00% <ø> (ø)
src/ast/nodes/index.ts	100.00% <ø> (ø)
src/Graph.ts	98.72% <100.00%> (ø)
src/Module.ts	98.90% <100.00%> (+<0.01%)	⬆️
src/ast/nodes/LogicalExpression.ts	98.75% <100.00%> (+0.01%)	⬆️

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