Better `TOML` libs -> `tomlkit` for style, `tomli(-w)` for speed

[goodboy]

Since we already had to roll our own based on writing a particular
styled .clears table to the pps.toml file, this is a task to
choose the best (combo of) lib(s).

Here's the verbatim bullet-task breakout from #345:

• after much pain and anguish getting
  the toml encoder to output things sanely, i think it's just worth
  writing or switching to a super fast custom encoder that writes
  adhoc-ly in the format we want for positions entries in pps.toml,
  the reader-writer separation is already what
  tomli does (the fastest pure py reader soon to land in the stdlib) and
  then we can just drop toml outright and worry about getting a general encoder later.

• support better indentation
  per broker-account for better readability,
  indented tables per broker-account would
  be super nice if possible

  • see tomlkit below which supports this -> https://github.com/pikers/tomlkit/blob/writing_docs_tweaks/tomlkit/items.py#L1644
  • see our PR adding an indent control to Array.multiline()
    Support Decimal and MutableMapping codecs, add a multiline-Array indent control python-poetry/tomlkit#294

---

Turns out there's been a bunch of project updates in the space 🙏🏼,

• tomlkit: from the poetry/pendulum auth:
  https://github.com/sdispater/tomlkit and is based on a rust lib

  • contains multi-line array writing: https://github.com/pikers/tomlkit/blob/writing_docs_tweaks/tomlkit/items.py#L1122
  • supports inline table rendering: https://github.com/pikers/tomlkit/blob/writing_docs_tweaks/tomlkit/items.py#L1122
  • we can now work off our own fork: https://github.com/pikers/tomlkit
    • needs Decimal input support: Support Decimal serialization? python-poetry/tomlkit#288
    • needs bidict input support: Support bidict inputs? python-poetry/tomlkit#289

• msgspec.toml now exists :party: which means we can natively render
  our msgs and structs easily!

  • uses tomli(-w) underneath so using that probably makes the most
    sense for our speed solution.
  • https://jcristharif.com/msgspec/install.html#toml
  • https://jcristharif.com/msgspec/api.html#toml
  • https://jcristharif.com/msgspec/supported-types.html#datetime

• a list of other alt libs that we prolly won't use but figured might as
  well put them here just in case:

  • pytomlpp c++ wrapped parser: https://bobfang1992.github.io/pytomlpp/pytomlpp.html
  • toml-w, stdlib's toml sibling writer lib: https://github.com/hukkin/tomli-w#does-tomli-w-support-writing-documents-with-comments-or-custom-whitespace
    • has Decimal support which i don't think is in tomlkit: https://github.com/hukkin/tomli#construct-decimaldecimals-from-toml-floats

[goodboy]

personal todo: Need to link our PR for inline array comment config support and possibly open an issue to support passing through such inputs to .item.array()

[goodboy]

Linking in tomlkit issues we need in order for us to be able to use that lib:

• Support Decimal serialization? python-poetry/tomlkit#288
• Support bidict inputs? python-poetry/tomlkit#289
• Add indent control for multi-line Array python-poetry/tomlkit#290