Clarify and reuse proper LUKS keys terminology consistenty in doc

[tlaurion]

The keys page (https://osresearch.net/Keys/) lists 4 keys related to disks but the docs include 10 different terms.

officially listed related to drive/disk

• TPM disk encryption key
• Disk recovery key
• LUKS disk encryption key
• Disk Unlock Key passphrase prompt output

terms used in docs

TPM disk encryption key:

• keys.md =>1
• configuring-keys.md: => 1

Disk recovery Key:

• keys.md => 4
• install-os => 4

LUKS disk encryption key:

• keys.md => 1

Disk encryption key without explicit LUKS/TPM:

• keys.md => 4
• upgrading.md => 1

Disk encryption recovery key:

• upgradigng.md => 1

Disk Key:

• faq.md => 2
• install-os.md => 1
• upgrading.md => 2

TPM disk unlock key:

• keys.md => 1
• install-os.md => 1

Disk unlock key passphrase:

• keys.md => 3

Disk unlock key:

• keys.md => 4
• install-os.md => 4

TPM sealed drive keys:

• heads-threat-model.md => 1

JT changes

After I worked on the docs it is mostly the same but a few changed

TPM disk encryption key: SAME

Disk recovery Key:

• keys.md => same
• install-os => same
• upgrading.md => 2

LUKS disk encryption key: SAME

Disk encryption key without explicit LUKS/TPM:

• keys.md => SAME
• configuring-keys.md => SAME
• upgrading.md => 0

Disk encryption recovery key: NONE

Disk Key:

• faq.md => same
• install-os.md => same
• upgrading.md => 1 (was 2)

TPM disk unlock key: SAME

Disk unlock key passphrase:

• keys.md => same
• upgrading.md => 1

Disk unlock key:

• keys.md => SAME
• install-os.md => SAME
• recoveryshellmd => 1
• upgrading.md => 1

TPM sealed drive keys: SAME

@tlaurion Which of the listed keys in keys.md should be mentioned in the paragraph in upgrading.md? If the keys that should be mentioned are not listed in keys.md I will add as part of this change.

Originally posted by @jtmoree-github-com in #71 (comment)

[tlaurion]

Context and precisions: #71 (comment)