tests: fix codecov coverage showing as failing when it's within expected OS-dependent variability + reduce green threshold to 80%

Signed-off-by: Stephen L. <lrq3000@gmail.com>

Author: lrq3000

codecov.yml

@@ -1,7 +1,16 @@
 coverage:
+  precision: 0			# 0 decimals of precision
+  round: nearest        # Round to nearest precision point
+  range: "50...80"		# red -> yellow -> green
+
   status:
     project:
       default:
         # basic
         target: auto
         removed_code_behavior: fully_covered_patch  # see: https://about.codecov.io/blog/new-codecov-setting-removed-code-behavior/
+        threshold: 1%		# allow 1% coverage variance, because depending on the run, different OSes results are uploaded for each run and some code is OS-specific, so this is it's within expected OS-dependent variability
+
+    patch:
+      default:
+        threshold: 1%		# allow 1% coverage variance