Flash Unit and HDA Flowsheet Tutorial Revisions to reflect changes to initialization and scaling updates as well as some overall improvements

[tannerpolley]

(From #143)

For the Flash Unit Model tutorial, changes include:

• Update to initialization
• Added scaling features for some variables
• Revised some language
• Improved overall structure and flow
• • Many other small changes

For the HDA Flowsheet Tutorial, changed include:

• Added Feed and Product unit models to improve the readability of the stream reports and align with current flowsheet standards
• Added full manual flowsheet initialization tutorial
• Added a AutoScaler method for a basic scaling step
• Revised overall structure and readability of many sections
• Many other small changes

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📚 Documentation preview 📚: https://idaes-examples--144.org.readthedocs.build/en/144/

[dallan-keylogic]

This PR is waiting on IDAES/idaes-pse#1643

[dallan-keylogic]

Now waiting on IDAES/idaes-pse#1646 , but also we might want to use a different set of state variables, FpcTP has issues with degeneracy when a phase disappears.

[ksbeattie]

@tannerpolley do you have time to look into this, perhaps restarting with a new PR?