Modular deps for binding and render

[sapk]

Following the similar pattern as sql drivers.
I extract xml, json, msgpack, protobuf and yaml into separate module.
This PR may break compat with previous versions.

For example: https://github.com/sapk-fork/gin-examples/blob/test-modular/basic/main.go

I think we can maybe re-add json and xml as default.

Related #1847 (issue) & #1852 (previous non-breaking solution)

[sapk]

For details:

• Context function calls are unchanged
• If the need module is not loaded it will panic for method like (c *Context) MsgPack or (c *Context) BindYAML(obj interface{})

[codecov]

Codecov Report

Merging #1856 into master will increase coverage by 0.49%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1856      +/-   ##
==========================================
+ Coverage   98.65%   99.14%   +0.49%     
==========================================
  Files          41       30      -11     
  Lines        2149     1991     -158     
==========================================
- Hits         2120     1974     -146     
+ Misses         18       11       -7     
+ Partials       11        6       -5

Impacted Files	Coverage Δ
gin.go	99.1% <ø> (ø)	⬆️
binding/uri.go	100% <100%> (ø)	⬆️
render/render_17.go	100% <100%> (ø)
render/render.go	100% <100%> (ø)	⬆️
binding/form.go	100% <100%> (ø)	⬆️
context.go	98.38% <100%> (ø)	⬆️
mode.go	100% <100%> (+9.09%)	⬆️
render/html.go	100% <100%> (ø)	⬆️
binding/query.go	100% <100%> (ø)	⬆️
render/reader.go	100% <100%> (ø)	⬆️
... and 6 more

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[dmarkham]

@sapk 👏

For example: https://github.com/sapk-fork/gin-examples/blob/test-modular/basic/main.go

I kinda like the way this feels only opting into what you want really nice 👍

I think we can maybe re-add json and xml as default.

I do like the idea of the "builtins" being there by default. But would that allow the user to replace the xml/json with a different (faster) binding/render for json/xml if we are including it by default?

I'm really interested in the core teams thoughts on this idea is!

👍 on the user's interface.
I'm still looking at the code to get a better feel for how you pulled this off.

If everyone likes this direction have a few chores like Docs, examples, benchmark, alloc's, etc.

[sapk]

@dmarkham Yes you can load a module that fill the same id in the respective common List to be call in place of the gin one.
If you want to already use a custom binding or render this is already possible with context method MustBindWith/ShouldBindWith and Render that just need a object that provide the respective interfaces.

[zzjin]

any update discuss?