Enforce branch coverage in workflow (set limit on uncovered branches)

[skliper]

Is your feature request related to a problem? Please describe.
#1114 gets us down to 4 uncovered branches (with issues for each), need to enforce so this doesn't slip w/ future updates.

Describe the solution you'd like
Workflow currently checks for 100% line coverage:

osal/.github/workflows/local_unit_test.yml

Lines 35 to 41 in f11d049

	- name: Confirm 100% line coverage
	run: |
	if [[ `grep -A 3 "Overall coverage rate" lcov_out.txt | grep lines` != *"100.0%"* ]]; then
	grep -A 3 "Overall coverage rate" lcov_out.txt
	echo "Lacks 100.0% line unit test coverage"
	exit -1
	fi

Add check of branches, suggesting reading in the branches*(AAA of BBB branches) and confirming BBB-AAA <= 4 (suggesting the bash math support to keep things simple).

Describe alternatives you've considered
Minimum % coverage is somewhat weak since it doesn't really catch if you add more uncovered branches (as long as you add enough covered ones also). Hard count check is better. Really getting to 100% is even better, but we aren't there yet.

Additional context
None

Requester Info
Jacob Hageman - NASA/GSFC

[nmullane]

I'll start working on this.