Add execprocess debug messages

[dragonstyle]

Sample:

$ quarto render --log-level debug 2>&1 | grep -i "\[execProcess\]"
[execProcess] which git
[execProcess] Success: true, code: 0
[execProcess] git rev-parse
[execProcess] Success: false, code: 128
[execProcess] /Users/cool-user/dev/package/dist/bin/tools/x86_64/dart-sass/sass /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/df54678c.scss /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/sass/aaecd917b9d237aa39e15a02e860d546.css --style compressed --quiet --load-path=/Users/cool-user/dev/src/resources/formats/html/bootstrap/dist/scss --load-path=/Users/cool-user/dev/src/resources/formats/html/bslib/bslib-scss
[execProcess] Success: true, code: 0
[execProcess] /Users/cool-user/dev/package/dist/bin/tools/x86_64/pandoc +RTS -K512m -RTS --defaults /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-defaultsc3b64472.yml /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-input031a71f4.md --metadata-file /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-metadatab4990235.yml --verbose --trace --data-dir /Users/cool-user/dev/src/resources/pandoc/datadir
[execProcess] Success: true, code: 0
[execProcess] /Users/cool-user/dev/package/dist/bin/tools/x86_64/pandoc +RTS -K512m -RTS --defaults /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-defaults02c7c01d.yml /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-input34b0ec5e.md --metadata-file /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-metadata58c5ecb6.yml --verbose --trace --data-dir /Users/cool-user/dev/src/resources/pandoc/datadir
[execProcess] Success: true, code: 0
[execProcess] /Users/cool-user/dev/package/dist/bin/tools/x86_64/pandoc +RTS -K512m -RTS --defaults /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-defaults7a10b4d5.yml /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-input6f9be3d9.md --metadata-file /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-metadata0f427806.yml --verbose --trace --data-dir /Users/cool-user/dev/src/resources/pandoc/datadir
[execProcess] Success: true, code: 0
[execProcess] /Users/cool-user/dev/package/dist/bin/tools/x86_64/pandoc +RTS -K512m -RTS --defaults /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-defaults262b5efb.yml /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-inputa845f63d.md --metadata-file /var/folders/xd/yz194wns70n2zknfrt5l0v0m0000gr/T/quarto-session1d948518/2783de1a/quarto-metadataa01728da.yml --verbose --trace --data-dir /Users/cool-user/dev/src/resources/pandoc/datadir
[execProcess] Success: true, code: 0