add UT for TccAnnotationProcessor class

[slievrly]

https://app.codecov.io/gh/apache/incubator-seata/blob/2.x/spring%2Fsrc%2Fmain%2Fjava%2Forg%2Fapache%2Fseata%2Fspring%2Ftcc%2FTccAnnotationProcessor.java

[OmCheeLin]

Please assign it to me, I would like to work on this.

[slievrly]

@OmCheeLin Looking forward to your PR.