[browsable] Add treemap v6 visualization in RBrowser for ntuples

[magnustymoteus]

This Pull request:

Changes or fixes:

This PR adds the following functionality

• Use ROOTTreeMap library in browsable by including it in gui/browsable/CMakeLists.txt
• Visualization node in the RBrowser that paints treemap of the corresponding RNTuple on click

Checklist:

• tested changes locally
• updated the docs (if necessary)

[linev]

Minor remark - there are files without new line at the end

[github-actions]

Test Results

    20 files      20 suites   3d 17h 57m 54s ⏱️
 3 663 tests  3 658 ✅   0 💤 5 ❌
71 547 runs  71 296 ✅ 246 💤 5 ❌

For more details on these failures, see this check.

Results for commit 235bbcd.

♻️ This comment has been updated with latest results.

[magnustymoteus]

Added newline to the changed files at the end