Handle PowerShell version support drop in a dedicated breaking-change item

[lipkau]

Problem

The ongoing Pester v5 migration PR is currently mixed with a potentially breaking compatibility change (raising the module minimum PowerShell version and support policy updates).

Combining migration hardening and support-floor changes increases release risk and review complexity.

Proposal

Move the PowerShell support-floor change into a dedicated backlog item and implementation PR.

That follow-up should include manifest compatibility changes, CI matrix policy updates, and explicit release communication for downstream users.

Acceptance criteria

• ConfluencePS Pester v5 migration PR ships without dropping existing PowerShell support contract.

• A dedicated PR updates the support floor intentionally (manifest and CI policy aligned).

• Dedicated support-drop implementation removes Set-TlsLevel usage from Invoke-Method and removes the Set-TlsLevel private helper.

• Release/changelog notes clearly call out the breaking change and migration guidance.

• CI coverage reflects the new support policy after the dedicated PR lands.

• Simplify duplicate-case JSON handling from Fix duplicate-case JSON parsing in Invoke-Method #235 by removing legacy compatibility fallback and using ConvertFrom-Json -AsHashtable directly once legacy PowerShell support is dropped.

[lipkau]

Added scope note: Set-TlsLevel removal is deferred and tracked under this breaking-change item; PR #234 was closed to keep current support behavior unchanged for now.