refactor: assets module form cleanup (backport #52393)

[khushi8112]

UI / UX Improvements

• Migrated is_existing_asset, is_composite_asset, and is_composite_component from multiple checkboxes to a single select field for clearer intent and mutual exclusivity. Also wrote patch for this.
• Moved calculate_depreciation out of the Depreciation tab into the Details section.
  The Depreciation tab is now shown only when depreciation is enabled, reducing visual noise.
• Removed or hid unused and rarely used fields (e.g. item_name, asset_owner) to simplify the form.
• Reorganized action buttons for better usability:
  • Grouped buttons under Create, Actions, and View for quicker access and consistency.
• Cleaned up Asset Capitalization and Asset Repair forms:
  • Removed unused fields related to the deprecated decapitalization flow.
  • Reorganized fields to improve layout and readability.

Overall, this improves clarity, reduces clutter, and makes asset-related workflows easier to follow without changing existing behavior.

---

Manual backport of pull request #52393

[codecov]

Codecov Report

❌ Patch coverage is 91.83673% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.41%. Comparing base (5c48f74) to head (7b44e41).
⚠️ Report is 7 commits behind head on version-16-hotfix.

Files with missing lines	Patch %	Lines
...eport/fixed_asset_register/fixed_asset_register.py	0.00%	3 Missing ⚠️
.../asset_capitalization/test_asset_capitalization.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##           version-16-hotfix   #52999      +/-   ##
=====================================================
- Coverage              79.42%   79.41%   -0.01%     
=====================================================
  Files                   1182     1182              
  Lines                 123971   123954      -17     
=====================================================
- Hits                   98459    98443      -16     
+ Misses                 25512    25511       -1     

Files with missing lines	Coverage Δ
...nts/doctype/accounting_period/accounting_period.py	82.35% <100.00%> (ø)
erpnext/assets/dashboard_fixtures.py	0.00% <ø> (ø)
erpnext/assets/doctype/asset/asset.py	83.42% <100.00%> (ø)
erpnext/assets/doctype/asset/depreciation.py	80.60% <100.00%> (ø)
erpnext/assets/doctype/asset/test_asset.py	99.49% <100.00%> (ø)
...ctype/asset_capitalization/asset_capitalization.py	85.34% <100.00%> (-0.43%)	⬇️
...ation_schedule/test_asset_depreciation_schedule.py	100.00% <ø> (ø)
...t/assets/doctype/asset_repair/test_asset_repair.py	100.00% <100.00%> (ø)
.../asset_capitalization/test_asset_capitalization.py	88.41% <88.88%> (+0.15%)	⬆️
...eport/fixed_asset_register/fixed_asset_register.py	0.00% <0.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.