FORMS-27300: log unresolved form asset for "Item not available" draft/submission entries

[ashnasingh101]

Problem

Forms Portal lists an "Item not available" placeholder in Drafts/Submissions when a
draft/submission record's form cannot be resolved on the current environment (form deleted or
unpublished here, or the record originates from another environment sharing the same store).
When this happens, DraftsAndSubmissionsImpl.getItem() silently falls back to the placeholder
with no server-side signal, so the entry is impossible to triage from logs.

Root cause

In getItem(), when resourceResolver.getResource(formAssetPath) returns null, the method
falls through to the hardcoded "Item not available" placeholder and still adds the item to the
list — with no logging on that branch.

Fix

Add an INFO log on the null-resource branch capturing type, id, formPath and the resolved
asset path, so the placeholder entry can be traced and its cause (deleted-here vs. cross-environment
record) identified from logs. No behavior change — the item is still listed exactly as before.

Tests

• New unit test testFormAssetNotResolvable covering the previously-untested null-resource branch:
  asserts the placeholder title/description and null form link.
• DraftsAndSubmissionsImplTest green (7/7); bundle compiles.