Dynamic directive arguments

[yyx990803]

Implementation per vuejs/rfcs#4

[codecov-io]

Codecov Report

Merging #9373 into dev will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev    #9373      +/-   ##
==========================================
- Coverage   97.34%   97.29%   -0.05%     
==========================================
  Files         107      108       +1     
  Lines        4551     4583      +32     
==========================================
+ Hits         4430     4459      +29     
- Misses        121      124       +3

Impacted Files	Coverage Δ
src/compiler/helpers.js	100% <100%> (ø)	⬆️
src/compiler/codegen/events.js	100% <100%> (ø)	⬆️
src/core/instance/render-helpers/index.js	100% <100%> (ø)	⬆️
src/compiler/codegen/index.js	100% <100%> (ø)	⬆️
src/compiler/parser/index.js	98.89% <100%> (ø)	⬆️
.../core/instance/render-helpers/bind-dynamic-keys.js	100% <100%> (ø)
src/core/instance/render-helpers/check-keycodes.js	70% <0%> (-30%)	⬇️
src/core/vdom/helpers/normalize-scoped-slots.js	94.11% <0%> (-0.33%)	⬇️
... and 3 more

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