fix(crosstab): Create one channel per instance

[alecklandgraf]

to: @milesj @stefhatcher @hayes @alecklandgraf

Description

crosstab was creating new BroadcastChannels at each on, off, and emit method call.

Motivation and Context

Crosstab wasn't working as expected after the previous change.

Testing

Added test

Screenshots

N/A

Checklist

• My code follows the style guide of this project.
• I have updated or added documentation accordingly.
• I have read the CONTRIBUTING document.

[airbnb-bot]

Size Changes

Package	Diff	ESM	Prev ESM	CJS	Prev CJS
core	+0.0%	549.33 KB	549.27 KB	688.82 KB	688.76 KB

Compared to master. File sizes are unminified and ungzipped.

View raw build stats

Previous (master)

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    "lib": 14147
  },
  "app-shell": {
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    "lib": 19874
  },
  "composer": {
    "esm": 68247,
    "lib": 101805
  },
  "core": {
    "esm": 562457,
    "lib": 705295
  },
  "forms": {
    "esm": 35672,
    "lib": 47577
  },
  "icons": {
    "esm": 156355,
    "lib": 205626
  },
  "layouts": {
    "esm": 15298,
    "lib": 20770
  },
  "metrics": {
    "esm": 5467,
    "lib": 7729
  },
  "test-utils": {
    "esm": 4279,
    "lib": 5937
  }
}

Current

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    "lib": 14147
  },
  "app-shell": {
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    "lib": 19874
  },
  "composer": {
    "esm": 68247,
    "lib": 101805
  },
  "core": {
    "esm": 562515,
    "lib": 705353
  },
  "forms": {
    "esm": 35672,
    "lib": 47577
  },
  "icons": {
    "esm": 156355,
    "lib": 205626
  },
  "layouts": {
    "esm": 15298,
    "lib": 20770
  },
  "metrics": {
    "esm": 5467,
    "lib": 7729
  },
  "test-utils": {
    "esm": 4279,
    "lib": 5937
  }
}