make processor state explicit in platform properties

This avoids the need to use @-notation when establishing platform
properties (e.g., in facts about ideal schedules).

Thanks to Maxime for the suggestion.
6 jobs for master in 4 minutes and 53 seconds
Status Job ID Name Coverage
  Build
passed #44452
1.9.0-coq-8.10

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passed #44451
1.9.0-coq-8.9

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passed #44453
allowed to fail
1.9.0-coq-dev

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  Process
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doc

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passed #44456
proof-length

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validate

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