Remove template specialization for toMsg functions

[jacobperron]

Resolves #176

Before, the compiler was preferring the overloaded function:

geometry2/tf2_geometry_msgs/include/tf2_geometry_msgs/tf2_geometry_msgs.h

Lines 397 to 398 in 71b0542

	inline
	geometry_msgs::msg::Transform toMsg(const tf2::Transform& in)

instead of the template specialization. I tried to change the overload into a template specialization, but then we run into the error that the compile can't deduce the second template parameter (ie. the return type).

I'm not sure if this is an ideal fix, or if instead we should go with template specialization (I'm not sure how we were/are benefiting from this), which requires the user to be explicit:

auto msg = tf2::toMsg<tf2::Stamped<tf2::Transform>, geometry_msgs::msg::TransformStamped>(tf_stamped);

I've also went ahead and made the change for stamped quaternions, which have the same bug.

[jacobperron]

Testing packages that depend on tf2_geometry_msgs:

• Linux
• Linux-aarch64
• macOS
• Windows

[sloretz]

LGTM with a recommendation to remove the templated declarations of toMsg() and fromMsg() in tf2/convert.h since they're no longer being used here.

I'm not sure if this can be backported. If a compiler chooses to ignore inline, I think the mangled name on the functions is changed when these become overloads instead of specializations.

[jacobperron]

@tfoote Before I merge this, maybe you can shed some light on if template specialization is required or if switching to overloads is fine.

[jacobperron]

@sloretz I think you're right that this is not eligible for backport, but users can still workaround the issue by explicitly providing template arguments.

I've rebased to get the latest changes and I've removed the last occurrence of the template specialization for fromMsg in tf2_geometry_msgs (499afbd). I've also updated the tests to use tf2::convert now that it is available (143e90d). PTAL

[jacobperron]

recommendation to remove the templated declarations of toMsg() and fromMsg() in tf2/convert.h since they're no longer being used here.

Since the templated declarations may be used elsewhere (outside of this repo), it might be better to leave them for now.

[jacobperron]

Rerunning after the rebase:

• Linux
• Linux-aarch64
• macOS
• Windows

[nuclearsandwich]

@jacobperron removed this from backport consideration since it is not ABI compatible.