Return HardLimitBytes from GCMemoryInfo.TotalAvailableMemoryBytes (#25437)
* Add property HardLimitBytes to GCMemoryInfo
This adds a new property HardLimitBytes.
Unlike TotalAvailableMemoryBytes,
this will reflect an explicitly set COMPLUS_GCHeapHardLimit.
It will also reflect the fraction of a container's size that we use,
where TotalAvailableMemoryBytes is the total container size.
Normally, though, it is equal to TotalAvailableMemoryBytes.
Fix #38821
* Remove HardLimitBytes; have TotalAvailableMemoryBytes take on its behavior
* Fix typos
* Separate total_physical_mem and heap_hard_limit
so we can compute highMemoryLoadThresholdBytes and memoryLoadBytes
* Do more work in gc.cpp instead of Gc.cs
* Consistently end names in "Bytes"