*  add RangeSectionMap docs

*  exhaustively test RangeSectionMap.EffectiveBitsForLevel

*  fix lookup in RangeSection.Find

    RangeSectionLookupAlgorithm.FindFragment finds the slot containing the range section fragment pointer.
    Have to dereference it once to get the actual RangeSectionFragment pointer from the slot.

    This "worked" before because RangeSectionFragment.Next is at offset 0, so the first lookup would have a garbage range, so we would follow the "next" field and get to the correct fragment

*   make a testable RangeSectionMap.FindFragmentInternal

*   brief nibble map summary

*   [cdac] Implement NibbleMap lookup and tests

    The execution manager uses a nibble map to quickly map program counter
    pointers to the beginnings of the native code for the managed method.

    Implement the lookup algorithm for a nibble map.

    Start adding unit tests for the nibble map

    Also for testing in MockMemorySpace simplify ReaderContext, there's nothing special about the descriptor HeapFragments anymore.  We can use a uniform reader.

*   NibbleMap: fix bug and add test

    Previously we incorrectly computed the prior map index when doing the backward linear search

*   [testing] display Target values in hex in debugger views

*   MockMemorySpace: simplify ReaderContext

    there's nothing special about the descriptor HeapFragments anymore.  We can use a uniform reader

*   refactor ExecutionManager

*   ExecutionManager contract

    the presence of RangeSection.R2RModule is a discriminator for whether we're looking at EE code or R2R code

*   WIP NibbleMap

*   WIP JitCodeToMethodInfo

*   WIP RangeSectionMap

The EECodeInfo includes the relative offset (given ip - start of method) so it's not ok to share for different code pointers into the same method

…lazy

Co-authored-by: Elinor Fung <elfung@microsoft.com>