Expand templates in checksum keys

[Micket]

There are more cases for things that do nested dicts with arch specific binary source tarballs. I started changing those as well, but there were a lot and it seems to work anyway, so i'm not sure if we should "fix" those as well.
They are all cases where a normal --inject-checksums wouldn't work (due to multiple source variants).

edit: fixes #22090

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 27 out of 27 (27 easyconfigs in total)
node3509.doduo.os - Linux RHEL 8.8, x86_64, AMD EPYC 7552 48-Core Processor, Python 3.6.8
See https://gist.github.com/boegel/bb13c02dcf4915cfce1955fd3a1d1aec for a full test report.

edit: this was using only --fetch, but that includes verifying of checksums

[boegel]

Test report by @boegel
FAILED
Build succeeded for 0 out of 1 (1 easyconfigs in total)
node3509.doduo.os - Linux RHEL 8.8, x86_64, AMD EPYC 7552 48-Core Processor, Python 3.6.8
See https://gist.github.com/boegel/f49355993ea069c0af260d37c9f69ada for a full test report.

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in total)
node3509.doduo.os - Linux RHEL 8.8, x86_64, AMD EPYC 7552 48-Core Processor, Python 3.6.8
See https://gist.github.com/boegel/b40d719cde503292ba71b5184ff27fb5 for a full test report.