Gradle: avoid cross-configuration and enable configuration-on-demand

[Konicai]

configure-on-demand, decoupled projects, and parallel projects are documented on Gradle: Configure On Demand. it's a good read.

Decoupling is necessary for usage of configure-on-demand or parallel execution to not result in flawed build outcomes. The previous link does not mention that the common usage of allprojects {} and subprojects {} to share build logic results in coupling, but it is mentioned and denounced on Gradle: Sharing Build Logic between Subprojects.

Changes that should allow enabling configure-on-demand, and improve the current use of parallel execution:

• usage of allprojects {} and subprojects {} has been removed
• the plugin applications performed in those blocks have been moved to respective project scripts

Changes for the sake of cleanup:

• geyser.platform-conventions now handles property expansion of platform files (rather than geyser.base-conventions)
  • previously its only purpose was applying geyser.publish-conventions
• geyser.modded-conventions now also applies geyser.platform-conventions
• geyser.build-logic has been removed in favour of geyser.base-conventions
• lombok was not previously used in api, but has now been also removed from the classpath
• Gradle convention: build-logic module renamed to buildSrc