[code-reflection] Integrated: Hat implement buffer minimization

[Gary Frost]

Looks like lots of changes, but mainly moved files from hat/hat to hat/hat-core.  

This free's up the shell script 'namespace' so I can add `hat` as a script for builds and sanity checks. 

Got rid of bash files for sanity checking and for building.  We should be using `java @bldr/bld`

Synced docs with these changes. 

The life demo now correctly displays Generations Per Second and more code is shared between the jextract and hat execution paths.

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Commit messages:
 - moved hat -> hat-core dir (to free up hat as a command name)  and modified iml, bld and docs
 - Moved SevenSegmentDisplay to hat.util.ui (so we can use it in other examples)
 - Finally we have correct numbers
 - Add seven seg displays to life
 - We can now add string markers to the profile.

Changes: https://git.openjdk.org/babylon/pull/342/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=342&range=00
  Stats: 2020 lines in 157 files changed: 373 ins; 1448 del; 199 mod
  Patch: https://git.openjdk.org/babylon/pull/342.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/342/head:pull/342

PR: https://git.openjdk.org/babylon/pull/342