v0.21.11

Turing v0.21.11

Diff since v0.21.10

Closed issues:

• Getting the preconditioner/checking that it is functional (#1860)
• Libtask error when using PG (#1873)
• VarInfo internal error with MH (#1874)
• Console logging of sampling broken (#1875)

Merged pull requests:

• Use LogDensityProblems instead of gradient_logp (#1877) (@devmotion)
• Update gibbs.jl (#1879) (@yebai)
• Remove outdated and unused Stan interface and tests (#1880) (@devmotion)