Addition of instance snapshots limits to the resource tab

[GeanJair]

Description

Currently, instance snapshot limits are not implemented in Apache CloudStack. Therefore, this PR adds the instance snapshots limits to the listResourceLimits API, and extends the GUI to display them for accounts, domains and projects in the Resources tab.

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)
• Build/CI
• Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Screenshots (if appropriate):

Account resources's tab

Domain resources's tab

Project resources's tab

How Has This Been Tested?

• I observed that the instance snapshot limit was now shown in the Resources tab of accounts, projects and domains.
• I created and deleted instance snapshots, to verified that the field was being incremented and decremented correctly.
• I tried to create more instance snapshots than the allowed and certified that the defined limit was correctly respected.