Remove ASM dependency and use Spring Core's instead

Depending on ASM itself can cause problems as it can clash with other
libraries' dependency on it. This commit updates
spring-boot-loader-tools to depend upon spring-core and use its
repackaged copy of ASM instead. Depending on spring-core also brings
with it the advantage of giving access to its various bits of utility
code.

spring-boot-maven-plugin has been updated to remove its ASM
exclusions as they will no longer clash with the version from
spring-boot-loader-tools

(59483608)