StringTemplates FormatProcessor fixes + test

[asotona]

---

Progress

• [ ] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• [x] Change must not contain extraneous whitespace
• [ ] Commit message must refer to an issue

Error

 ⚠️ The pull request body must not be empty.

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/amber pull/87/head:pull/87
$ git checkout pull/87

Update a local copy of the PR:
$ git checkout pull/87
$ git pull https://git.openjdk.org/amber pull/87/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 87

View PR using the GUI difftool:
$ git pr show -t 87

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/amber/pull/87.diff

[bridgekeeper[bot]]

:wave: Welcome back asotona! A progress list of the required criteria for merging this PR into templated-strings will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk[bot]]

:warning: @asotona a branch with the same name as the source branch for this pull request (templated-strings) is present in the target repository. If you eventually integrate this pull request then the branch templated-strings in your personal fork will diverge once you sync your personal fork with the upstream repository.

To avoid this situation, create a new branch for your changes and reset the templated-strings branch. You can do this by running the following commands in a local repository for your personal fork. Note: you do not have to name the new branch NEW-BRANCH-NAME.

$ git checkout -b NEW-BRANCH-NAME
$ git branch -f templated-strings 3f0f1bde1a11eb10fa259c12b880b31075497e33
$ git push -f origin templated-strings

Then proceed to create a new pull request with NEW-BRANCH-NAME as the source branch and close this one.