Draft: Bring ME0 to feature-parity

Description

As the title says, this MR aims at bringing the ME0 station to feature-parity in cmsgemos. In particular, that means:

• Implementing the S-bit rate scan (via the unified register hierarchy; see emu/0xbefe!143)
  • Update the recommended/supported firmware versions
• Implementing the environmental parameters monitoring via lpGBT ADC readouts

Additionally, misc cleanups and improvements are introduced in this MR:

• Introduction of the std::optional<T> in gemhardware (possible since the introduction of C++17)
• Checking of the GBTx/lpGBT serial number in the gem-check-layout-tree tool
• Avoidance of stalled data in the monitoring suite
  • Via the suppression of the magic 0xffffffff and 0xdeaddead values
• Clean up of the lpGBT-specific functions

Related Issue

How Has This Been Tested?

• GE1/1
• GE2/1
• ME0
  • Being used on the ME0 stack

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.