Enable gosec linter for golangci-lint

`gosec` linter is able to identify issues described in #6584

e.g.

$ git revert 54e95e6b88
[gosec dfc8ca1ec] Revert "fix Implicit memory aliasing in for loop"
 2 files changed, 2 deletions(-)

$ make check
+ proto-fmt
+ check
GOGC=75 golangci-lint run
containerstore.go:192:54: G601: Implicit memory aliasing in for loop. (gosec)
		containers = append(containers, containerFromProto(&container))
		                                                   ^
image_store.go:132:42: G601: Implicit memory aliasing in for loop. (gosec)
		images = append(images, imageFromProto(&image))
		                                       ^
make: *** [check] Error 1

I also disabled following two settings which prevent the linter to show a complete list of issues.

* max-issues-per-linter (default 50)
* max-same-issues (default 3)

Furthermore enabling gosec revealed many other issues. For now I blacklisted the ones except G601.

Will create separate tasks to address them one by one moving next.

Signed-off-by: Henry Wang <henwang@amazon.com>

.golangci.yml

@@ -11,12 +11,28 @@ linters:
     - vet
     - unused
     - misspell
+    - gosec
   disable:
     - errcheck
 
 issues:
   include:
     - EXC0002
+  max-issues-per-linter: 0
+  max-same-issues: 0
+
+linters-settings:
+  gosec:
+    # The following issues surfaced when `gosec` linter
+    # was enabled. They are temporarily excluded to unblock
+    # the existing workflow, but still to be addressed by
+    # by future works.
+    excludes:
+      - G204
+      - G305
+      - G306
+      - G402
+      - G404
 
 run:
   timeout: 8m