Make IceCap server tests more reliable

[egrimley-arm]

Problems we have seen include:

• A single test taking more than 30 minutes on GitHub with PROFILE=dev and passing (apparently).
• The entire server-test suite finishing in about 3 minutes on localci without PROFILE=dev and passing (apparently).
• Huge variation in how long a test run takes both on GitHub and on localci.

The command to run just the IceCap server tests is:

make -C workspaces/icecap-host test-server

[dominic-mulligan-arm]

I also saw this yesterday: on localci the icecap server-test seemed to hang indefinitely with PROFILE=dev on the main branch. There were a few diagnostic about allocating pages produced on the command line, but then it just seemed to loop forever, though I don't think I waited long enough to see whether 30 minutes would suffice for it to do anything...

[egrimley-arm]

In this run (https://github.com/veracruz-project/veracruz/runs/6211854461) there was one failure:
test_phase1_new_session timed out after 2400 s.

In this run (https://github.com/veracruz-project/veracruz/runs/6211990415) there was one failure:
test_phase1_init_destroy_enclave timed out after 2400 s.

There was different code in the two cases, but I don't think the differences are significant.
I think the failures are random.

[egrimley-arm]

In https://github.com/veracruz-project/veracruz/runs/6224096982 it's
test_phase2_random_source_no_data_no_attestation_unauthorized_key

(I'm doing "Re-run failed jobs". People might need to get used to using that button.)

[egrimley-arm]

Here we seem to have the same problem after #440 was applied:
https://github.com/veracruz-project/veracruz/runs/6311243609

[mathias-arm]

Here we seem to have the same problem after #440 was applied: https://github.com/veracruz-project/veracruz/runs/6311243609

It's a different issue. The changes in the draft PR make IceCap crash.