Update graph snapshot processing

[edelarua]

Closes #182

Merge after insightsengineering/tern#1158

This should standardize the generation of graph snapshots across different systems and hopefully fix the failing integration tests for graph snapshot differences.

Note: kmg01 snapshots will be fixed after g_km is refactored.

[github-actions]

Unit Tests Summary

    1 files  2 suites   1m 1s ⏱️
  24 tests 0 ✔️   24 💤 0 ❌
290 runs  0 ✔️ 290 💤 0 ❌

Results for commit a65ee12.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Performance Difference

Test Suite	$Status$	Time on main	$±Time$	$±Tests$	$±Skipped$	$±Failures$	$±Errors$
graph-snaps	💔	$7.99$	$+1.97$	$+4$	$+4$	$0$	$0$
markdown-snaps	💔	$50.31$	$+1.03$	$0$	$0$	$0$	$0$

Additional test case details

Test Suite	$Status$	Time on main	$±Time$	Test Case
graph-snaps	💔	$3.25$	$+2.36$	plot_v1
graph-snaps	💀	$0.16$	$-0.16$	plot_v1_and_v2
graph-snaps	💀	$0.09$	$-0.09$	table_v6

Results for commit 88f986c

♻️ This comment has been updated with latest results.

[Melkiades]

Amazing job Emily! I also read the main PR with rtables2gg. Fantastic! :)