Inline jmbr, smbr, tmbr

[krlmlr]

We agreed on inlining the three packages that now implement embr methods:

• jmbr
• smbr
• tmbr

I already did this for pmbr: 95d9cea .

Example for jmbr, substitute with smbr/tmbr as needed:

• In jmbr, rename R/*.R to R/jmbr-*.R and tests/testthat/test-*.R to tests/testthat/test-jmbr-*.R
• Copy over files to embr
• Add jmbr's strong dependencies as suggested dependencies here
• Make sure R CMD check succeeds
• Commit
• Implement a function that installs all of jmbr's strong dependencies with pak, using, e.g., "rjags?source" to install from source
• In jmbr, remove all methods (so that the NAMESPACE file becomes empty)
• Remove jmbr from poispkgs
• Archive https://github.com/poissonconsulting/jmbr/