Generate unit test for functions with variable semantics

[nathan-boulestin]

Is your feature request related to a problem? Please describe.
We declare functions with the variable semantics to make mocking a lot easier.
For example we will declare var MyFunc= func() instead of func MyFunc()
The commands for generating unit tests does not recognize this semantic as functions and does no generate any unit test template.

Describe the solution you'd like
I would like the commands for generating units tests to also work for the variable semantic.
So a function declared var MyFunc= func() would produce the same unit test as func MyFunc().

Describe alternatives you've considered
As an alternative I made a regex to convert functions to each declaration semantic using text replace:
var MyFunc= func() -> func MyFunc():
match: var ([a-zA-Z]*) = func(\([a-zA-Z\s\.\*]*\))
replace: func $1$2

func MyFunc() -> var MyFunc= func():
match: func ([a-zA-Z]*)(\([a-zA-Z\s\.\*]*\))
replace: var $1 = func$2

I have to convert the functions, use the generate unit tests command, and then convert back the functions semantic.

[suzmue]

We are planning to move the test generation feature into gopls (#1594).

The issue tracking the migration of tools is available in #1652.