cli-plugins: separate hook types from manager and refactor

[thaJeztah]

cli-plugins/manager: Plugin.RunHook: improve error message

Currently, the error was a plain "exit status 1"; make the error
message more informative if we need it :)

cli-plugins/manager: simplify ctx-cancel check

cli-plugins/manager: refactor for easier debugging

Extract the code inside the loop to a closure, so that we can more
easily set up debug-logging.

cli-plugins/manager: move HookPluginData to hooks.Request

Separate types used by plugins from the manager code.

cli-plugins/hooks: rename HookMessage to Response

cli-plugins/hooks: rename HookType to ResponseType

Rename the type to match the struct it's used for. Also;

• Fix the type of the NextSteps const
• Don't use iota for values; the ResponseType is used as
  part of the "wire" format, which means that plugins using
  the value can use a different version of the module code;
  using iota increases the risk of (accidentally) changing
  values, which would break the wire format.

cli-plugins/hooks: add JSON labels, omitzero

Add labels to define the expected casing and don't serialize
empty fields.

cli-plugins/hooks: move template utils separate from render code

These utilities are used by CLI-plugins; separate them from the render
code, which is used by teh CLI-plugin manager.

cli-plugins/hooks: update tests

• add basic unit-test for the template utilities
• make sure the template parsing tests test both the current
  template produced by the utilities, as well as a fixture
• rewrite the printer test to use fixtures
• use blackbox testing ("hooks_test")

cli-plugins/hooks: slight tweaks in templates

• use %q instead of manually quoting the string
• use %d instead of manually converting the number to a string

cli-plugins/hooks: detect if templating is needed

cli-plugins/hooks: limit maximum number of lines / messages

cli-plugins/hooks: update godoc

cli-plugins/hooks: add commandInfo type for templating

Define a local type for methods to expose to the template, instead of
passing the cobra.Cmd. This avoids templates depending on features
exposed by Cobra that are not part of the contract, and slightly
decouples the templat from the Cobra implementation.

cli-plugins/hooks: simplify templating formats

This allows for slighly cleaner / more natural placeholders, as it
doesn't require the context (.) to be specified;

• {{command}} instead of {{.Command}} or {{command .}}
• {{flagValue "my-flag"}} instead of {{.FlagValue "my-flag"}} or {{flagValue . "my-flag"}}`

cli-plugins/hooks: PrintNextSteps: slight cleanup

• skip aec to construct the formatting and use a const instead
• skip fmt.Println and write directly to the writer

- Human readable description for the release notes

Go SDK: cli-plugins/manager: deprecate `HookPluginData` and move to `cli-plugins/hooks.Request`
Go SDK: cli-plugins/hooks: deprecate `HookMessage ` and rebane to `cli-plugins/hooks.Response`
Go SDK: cli-plugins/hooks: deprecate `HookType` and rebane to `cli-plugins/hooks.ResponseType `

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 59.30233% with 35 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cli-plugins/hooks/template.go	64.10%	7 Missing and 7 partials ⚠️
cli-plugins/manager/hooks.go	51.72%	14 Missing ⚠️
cli-plugins/manager/plugin.go	0.00%	7 Missing ⚠️

📢 Thoughts on this report? Let us know!

[thaJeztah]

This one I was considering if we should perhaps drop the omitzero to make it usable as a discriminator (and more clearly have different responses in future if we need)

We should have a Type in Request as well, but that's for a follow-up.

Let me push that change, then we should be good to go.