Cancel outdated CI runs

[DavidBadura]

Adds a concurrency group to the CI workflows, so a new push to a pull request or branch cancels the runs still going for the previous commit instead of letting them finish for nothing. It uses the same group the app repositories already have (github.workflow plus head_ref || ref), so pull requests and branches never cancel each other. Release, notify and docs deploy workflows are left as they are.

[github-actions]

Hello 👋

Here are the most recent benchmark results, compared against 2.1.x. Time is the mode over the iterations in the its column, with the relative standard deviation in brackets.

StackHydrator

subject	revs	its	memory	base	current	diff
benchHydrate1Object	1000	5	1.855mb -21.23%	2.476μs (±1.28%)	2.488μs (±1.12%)	+0.46%
benchExtract1Object	1000	5	1.855mb -21.23%	2.779μs (±0.62%)	2.783μs (±1.47%)	+0.15%
benchHydrate1000Objects	3	5	1.855mb 0.00%	2.459ms (±2.35%)	2.441ms (±2.68%)	-0.70%
benchExtract1000Objects	3	5	1.855mb 0.00%	2.335ms (±0.47%)	2.347ms (±0.70%)	+0.52%

StackHydratorWithLazy

subject	revs	its	memory	base	current	diff
benchHydrate1Object	1000	5	1.855mb 0.00%	0.422μs (±3.87%)	0.411μs (±3.28%)	-2.68%
benchHydrate1ObjectTriggerInit	1000	5	1.855mb 0.00%	3.016μs (±0.79%)	3.018μs (±0.96%)	+0.08%
benchHydrate1000Objects	3	5	1.855mb 0.00%	399.983μs (±0.65%)	401.104μs (±0.90%)	+0.28%
benchHydrate1000ObjectsTriggerInit	3	5	1.855mb 0.00%	2.966ms (±1.90%)	2.970ms (±1.08%)	+0.13%

StackHydratorWithCryptography

subject	revs	its	memory	base	current	diff
benchHydrate1Object	1000	5	1.855mb 0.00%	3.613μs (±0.54%)	3.630μs (±1.47%)	+0.47%
benchExtract1Object	1000	5	1.855mb 0.00%	8.975μs (±0.24%)	9.011μs (±7.78%)	+0.40%
benchHydrate1000Objects	3	5	1.855mb 0.00%	3.587ms (±2.21%)	3.602ms (±0.96%)	+0.42%
benchExtract1000Objects	3	5	1.855mb 0.00%	8.328ms (±0.95%)	8.330ms (±1.32%)	+0.02%

This comment gets updated every time a new commit comes in.