Add Riemannian manifold HMC

[ErikQQY]

Add the Riemannian manifold HMC from "Riemann manifold Langevin and Hamiltonian Monte Carlo methods" which is implemented in the research directory but has not been merged into the package. Supersede #432 #437

[github-actions]

AdvancedHMC.jl documentation for PR #439 is available at:
https://TuringLang.github.io/AdvancedHMC.jl/previews/PR439/

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 33 lines in your changes missing coverage. Please review.

Project coverage is 78.31%. Comparing base (5a562e0) to head (567e2a8).

Files with missing lines	Patch %	Lines
src/riemannian/metric.jl	0.00%	21 Missing ⚠️
src/riemannian/hamiltonian.jl	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #439      +/-   ##
==========================================
+ Coverage   75.44%   78.31%   +2.86%     
==========================================
  Files          21       22       +1     
  Lines        1230     1185      -45     
==========================================
  Hits          928      928              
+ Misses        302      257      -45     

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