Fix clock constraints not affecting place_opt

[jerryz123]

Addresses #820.
TLDR: Previously, top-level clock constraints weren't read until pre-CTS. Now, they are read pre-placement, so clock-aware placement can be performed.

Related PRs / Issues
#820

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• Change to core Hammer
• Change to a Hammer plugin
• Other

Contributor Checklist:

• Did you set master as the base branch?
• Did you state the type-of-change/impact?
• Did you delete any extraneous prints/debugging code?
• (If applicable) Did you add documentation for the feature?
• (If applicable) Did you update the poetry.lock file if you updated the requirements in pyproject.toml?
• (If applicable) Did you add a unit test demonstrating the PR?
• (If applicable) Did you run this through the e2e integration tests?
• (If applicable) Did you update the submodules in e2e/ if this feature depends on updated plugins?

[harrisonliew]

Closes #820