Remove unnecessary inclusion of oopMap.hpp

oopMap.hpp is included by about 585 out of about 1000 .o files in HotSpot. In turn, it pulls in other complex headers such as vmreg.hpp, register.hpp and their cpu-dependent headers.

There are only 4 header files that include oopMap.hpp. All of these can be replaced for forward declarations.

According to https://github.com/iklam/tools/tree/main/headers

[before]

/jdk/src/hotspot$ whoincludes oopMap.hpp
scanning 585 oopMap.hpp
   2 found 553 method.hpp
   3 found 407 codeBlob.hpp
   4 found 262 debugInfoRec.hpp
   5 found 232 ciEnv.hpp
/jdk/src/hotspot$ whoincludes vmreg.hpp
scanning 597 vmreg.hpp
   2 found 585 oopMap.hpp
   3 found 281 location.hpp
   4 found 118 regmask.hpp
   5 found 109 registerMap.hpp
   ...
/jdk/src/hotspot$ whoincludes register.hpp
scanning 611 register.hpp
   2 found 611 register_x86.hpp
   3 found 597 vmreg.hpp
   4 found 364 assembler.hpp
   5 found 364 assembler_x86.hpp
   ...

[after]

/jdk/src/hotspot$ whoincludes oopMap.hpp
scanning 39 oopMap.hpp
   2 found 6 c1_LinearScan.hpp
/jdk/src/hotspot$ whoincludes vmreg.hpp
scanning 333 vmreg.hpp
   2 found 281 location.hpp
   3 found 181 sharedRuntime.hpp
   4 found 118 regmask.hpp
   5 found 109 registerMap.hpp
   ...
/jdk/src/hotspot$ whoincludes register.hpp
scanning 386 register.hpp
   2 found 386 register_x86.hpp
   3 found 364 assembler.hpp
   4 found 364 assembler_x86.hpp
   5 found 333 vmreg.hpp
   ...