Add support for Tectonic.toml

[PHPirates]

Fix #3773

Summary of additions and changes

• Requires pre-release version of Tectonic, tested with https://github.com/tectonic-typesetting/tectonic/releases/tag/continuous
• Runs -X build in the directory of the Tectonic.toml file if such a file is detected in any parent dir of the main file
• Puts files from inputs in the Tectonic.toml file in the same file set

How to test this pull request

[doc]
name = "main"
bundle = "https://relay.fullyjustified.net/default_bundle_v33.tar"
[[output]]
name = "main"
type = "pdf"
# Paths relative to ./src
inputs = [
    "main-preamble.tex",
    "main.tex",
]

Packages from main-preamble should be detected in main.tex