perf: optimize serializing renderBody & legacy widgets

[DylanPiercey]

Description

Optimizes serialization by doing the following:

• Legacy component marker is now a flag instead of a prop.
• input.renderBody now serializes as a flag instead of warp10Noop.
• extra serialized data is omitted if empty
• extra.r (renderBoundary) is removed since it is not in use.

This PR also contains a fix where is is possible to have a false negative when checking if the input changed across renders if removing an undefined property.

Checklist:

• I have read the CONTRIBUTING document and have signed (or will sign) the CLA.
• I have updated/added documentation affected by my changes.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Merging #1539 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1539      +/-   ##
==========================================
+ Coverage   90.57%   90.59%   +0.01%     
==========================================
  Files         356      356              
  Lines       12685    12705      +20     
==========================================
+ Hits        11490    11510      +20     
  Misses       1195     1195              

Impacted Files	Coverage Δ
...ges/marko/src/runtime/components/beginComponent.js	100.00% <ø> (ø)
.../src/runtime/components/init-components-browser.js	83.04% <ø> (ø)
packages/marko/src/runtime/components/util.js	91.30% <ø> (ø)
packages/marko/src/runtime/helpers/dynamic-tag.js	97.43% <ø> (ø)
...kages/marko/src/runtime/html/helpers/data-marko.js	100.00% <ø> (ø)
packages/marko/src/runtime/components/Component.js	95.86% <100.00%> (ø)
...kages/marko/src/runtime/components/ComponentDef.js	98.73% <100.00%> (+0.12%)	⬆️
packages/marko/src/runtime/components/index.js	97.22% <100.00%> (+0.41%)	⬆️
...runtime/components/legacy/defineRenderer-legacy.js	93.75% <100.00%> (ø)
...o/src/runtime/components/legacy/renderer-legacy.js	96.96% <100.00%> (-0.04%)	⬇️

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