Fix undeclared variables and inconsistent assignments, continued

[muzimuzhi]

See #22.

BREAKING CHANGE: Using an undefined template in \SetTblrTemplate now raises an error.

Deprecated \tl_case:N(TF) is not replaced with \token_case_meaning:N(TF) as the former was deprecated on 2022-05-23, relatively recently.

[lvjr]

In table-001.tlg, tabularray version number is removed but varwidth version number remains. Maybe it is a bug of l3build.

[muzimuzhi]

This PR supersedes #483, except for the \tl_case:N(TF) to \token_case_meaning:N(TF) replacement.

[muzimuzhi]

In table-001.tlg, tabularray version number is removed but varwidth version number remains. Maybe it is a bug of l3build.

varwidth uses a non-conventional version notation ("ver 0.92") while l3build only replaces the v<version> pattern. I've ignored all log lines produced when loading varwidth package.

Package: tabularray ....-..-.. v... Typeset tabulars and arrays with LaTeX3
Package: varwidth ....-..-.. ver 0.92;  Variable-width minipages

[lvjr]

Deprecated \tl_case:N(TF) is not replaced with \token_case_meaning:N(TF) as the former was deprecated on 2022-05-23, relatively recently.

This reminds me that it is needed to add something to doc about how many texlive releases are supported by tabularray.

[lvjr]

Maybe we can support four texlive releases (with all updates). For example, tabularray releases published in 2025 could be used in texlive 2022-2025 with latest updates.