GUI: Fix elements module for new canvas API

[Willy-JL]

What's new

• Use signed int32_t for coordinates and bigger size_t for width/height, according to new Canvas API
• Allows to use negative coordinates as intended by Canvas

Verification

• Can use negative coordinates for elements functions, such as drawing elements_slightly_rounded_frame() slightly off-screen to the left

Checklist (For Reviewer)

• PR has description of feature/bug or link to Confluence/Jira task
• Description contains actions to verify feature/bugfix
• I've built this code, uploaded it to the device and verified feature/bugfix

[hedger]

Please also update symbols for f18 (fbt TARGET_HW=18) so that both version numbers are equal.

[Willy-JL]

oh sure, my bad

[Willy-JL]

thanks for the additional fixes, works great!