Improve TPM event log for AEM

[krystian-hebel]

Affected component(s) or functionality
The component or functionality of TrenchBoot that is not working as expected.

AEM - TPM event log entries

Brief summary
A clear and concise summary of the bug.

Not all of the entries have a description, initial ones performed by early Xen code don't. On top of that, the form of description is different between legacy and UEFI, as the descriptions are made by different components - Xen for UEFI and GRUB for legacy boot mode.

Version
The version of the component or feature if available, otherwise NA.

v0.5.0

To Reproduce
Steps to reproduce the behavior:

1. Install AEM v0.5.0 under Qubes OS for legacy and UEFI
2. Boot with AEM enabled
3. Compare result of anti-evil-maid-dump-evt-log between both

Expected behavior
A clear and concise description of what you expected to happen.

All entries added by TrenchBoot (so no TXT ones) have Event field filled. The naming is consistent.

Actual behavior
What actually happened (instead of what you expected to happen).

aem_hw-aem_event-legacy.log
aem_hw-aem_event-uefi.log

Screenshots
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Additional context
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Solutions you've tried
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Relevant documentation you've consulted
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Related, non-duplicate issues
A list of links to other bug reports, feature requests, or tasks in the
trenchboot-issues tracker (or "none" if you didn't find any). Do not describe
any other unreported bugs, features, or tasks here.