Reorganize Iceberg connector documentation

[m57lyra]

Description

THERE ARE NO TECHNICAL CONTENT CHANGES TO EXISTING MATERIAL IN THIS PR

This PR is a follow-on to PR#15637. It reorganizes the Iceberg connector documentation to match the structure of the Hive connector documentation and, as with the Hive PR, does the following:

• Fixes problematic verb tenses as per Google Developer Style Guide (must use present tense only).
  These included would, should, could, needs to, will be; there were not many instances.
• Formats the few tables remaining in the old format to the list table format (and of course adds table titles).
• Adds intro blurbs where there were none for the following section headers:
  • Metastores
  • Security
  • Procedures (used same language as the Hive blurb)
  • Table properties (used same language as the Hive blurb)
  • View management (used same language as the Hive blurb)
  • Performance (used same language as the Hive blurb)
  • File formats (used same language as the Hive blurb)

Additional context and related issues

Here is a possibly helpful screen cap showing how the Iceberg doc org lines up with the Hive doc org now:

Release notes

(x) This is not user-visible or docs only and no release notes are required.
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( ) Release notes are required, with the following suggested text:

# Section
* Fix some things. ({issue}`issuenumber`)