KICAD7_TEMPLATE_DIR doesn't support multiple paths

Description

the environment variable KICAD7_TEMPLATE_DIR, when used to find templates, is not split by the path separator (: or ;)

this means that in a system where the outputs of the KiCad Symbols, Footprints and Templates libraries are installed in different paths,
one cannot provide both the fp-lib-table and sym-lib-table (which are searched for correctly in KICAD7_TEMPLATE_DIR)
and the path to the templates

Steps to reproduce

  1. install the Symbols, Footprints and Templates libraries in separate paths
    1. not somewhere KiCad knows to look for them, also don't have them installed in such a location already
  2. delete the cached library tables in ~/.config/kicad/7.99 or equivalent for your OS and version
  3. set the symbol and footprint environmental variables to the corresponding libraries
  4. set the KICAD7_TEMPLATE_DIR to something like /path/to/symbols/share/kicad/template:/path/to/footprints/share/kicad/template:/path/to/templates/share/kicad/template
  5. open the Project Template Selector (File -> New Project from Template...)
  6. see no templates

(the Nix package from Nixpkgs exhibits this issue if the system it's running on does not have the symbol/footprint/template libraries where KiCad looks for them)

KiCad Version

7.99 from 2023-05-18 
Application: KiCad x86_64 on x86_64

Version: 7.99.0-898d88cc11, release build

Libraries:
	wxWidgets 3.2.2
	FreeType 2.13.0
	HarfBuzz 7.2.0
	FontConfig 2.14.0
	libcurl/8.0.1 OpenSSL/3.0.8 zlib/1.2.13 brotli/1.0.9 zstd/1.5.5 libidn2/2.3.4 libssh2/1.10.0 nghttp2/1.51.0

Platform: Linux 6.3.2 x86_64, 64 bit, Little endian, wxGTK, , wayland

Build Info:
	Date: Jan  1 1980 00:00:00
	wxWidgets: 3.2.2 (wchar_t,wx containers) GTK+ 3.24
	Boost: 1.79.0
	OCC: 7.6.2
	Curl: 8.0.1
	ngspice: 37
	Compiler: GCC 12.2.0 with C++ ABI 1017

Build settings:
	KICAD_USE_EGL=ON
(KiCad 7.0.2 also affected)

Side Note

this seems like a typo
https://gitlab.com/kicad/code/kicad/-/blob/10574839836941ed84e8a5d149435e306fa02d47/common/settings/common_settings.cpp#L43