Plugin Import updates

[imhoffd]

This is an implementation of the plugin import proposal. To achieve consistent imports in each platform, I recommend we move the Plugins proxy from user code to plugin author code.

registerPlugin should be used to register implementations of plugins in each platform
registerWebPlugin will continue to work so people can continue using the plugin proxy and the web implementation (we can avoid a breaking change)

TODO

• add a compat.ts for legacy (PluginRegistry, etc.)

closes: #3306

[mlynch]

First pass looks good, where do the existing web plugins end up getting registered now? Or will that come w/ them being split out into separate packages?

[imhoffd]

registerWebPlugin got moved here: https://github.com/ionic-team/capacitor/pull/3305/files#diff-1cb8bd56af1537f63fe48eb4fd61aad0R85-R104

Existing plugins should continue working, with a console warning. We'll have to add an upgrade guide for plugins to switch to the new registerPlugin method so that the user can use the new imports across all platforms.

[mlynch]

I saw that but wasn't sure where the actual registration was happening anymore now that this line is gone: https://github.com/ionic-team/capacitor/pull/3305/files#diff-8aa3e4905a661a3f822d1f6cdf593c15L22

[imhoffd]

Oops, updated!

[mlynch]

I'm still missing where the actual merge/register is being called for the core web plugins? If it's not called somewhere explicitly then the web plugins won't be registered, right?

[imhoffd]

I can add it in, but we're going to be splitting out the plugins anyway in the next few days.

[mlynch]

Right that makes sense

[imhoffd]

Okay this is good to go. @jcesarmobile?