doc/radosgw: Small improvements in kmip.rst

doc/radosgw: Small improvements in kmip.rst

Major rewrite of the last section that is a copypasta from vault.rst:
- "engines" are relevant only to Hashicorp Vault and not KMIP
- leave only 1 copy of the 2 identical CLI examples
- talk about KMIP and not Vault, it is an alternative to Vault
Also fix other mention of "Vault" into "KMIP".

Auto-generate contents list instead of hardcoding it.

Use '=' in ceph.conf example, I believe ':' cannot be used.

Capitalize "Ceph", "Python", "KMIP", "OpenSSL", "PyKMIP" consistently.
Call it consistently "Ceph Object Gateway".
Format "pykmip" in italic when referring to the binary.
Hyphen in "PEM-encoded" along with capitalization.
Use double backticks for data.

Spell out a lonesome number "1" in text.
Fix typo "correspondent" to "corresponding".

Promptify CLI commands.

Use title case consistently in section titles.

Linkify mention of Ceph configuration file.

Signed-off-by: Ville Ojamo <14869000+bluikko@users.noreply.github.com>