go-fsck: collect package size info

[titpetric]

Go x/packages allows to collect size info for packages.

https://stackoverflow.com/questions/55132462/how-do-i-check-the-size-of-a-go-project

As a developer, I want to run go-fsck to achieve the following output:

• the package used
• number of symbols referenced (int)
• size of package in KB/MB

Runing go-fsck stats with a --package option should list the packages imported like so:

Import	Symbols	Size
github.com/evanphx/json-patch/v5	1	20KB

Symbols (1) column counts the number of distinct symbols being used from a package.

Using -v (verbose) should print something along the lines of:

Import	Symbol	Used
github.com/evanphx/json-patch/v5	DecodePatch (1)	20KB

The number in the brackets is the number of times a symbol is referenced, symbols are ordered descending by the number of uses. Packages may be sorted either by symbols used or by size.

Use case: find out little-used dependencies to remove.