golang: split src into separate packages

golang: split src into separate packages

Split misc sources and test data into separate packages. Reduces target
src package size by a third.

Move architecture-dependent generated source from src to the main
package.

Mark doc, misc, src and tests packages with PKGARCH:=all as they don't
have any architecture-specific files.

Fix stripping and strip compiler only.

Fixes: c137c382 ("golang: new packages")
Link: https://github.com/openwrt/packages/pull/28445
Suggested-by: Jeffery To <redacted>
Signed-off-by: George Sapkin <redacted>