[BOLT][CMake] Add merge-fdata to bolt component

Build and install `merge-fdata` tool as part of `bolt` component:
```
$ ninja bolt
# builds llvm-bolt, perf2bolt and merge-fdata

$ cmake --install . --component bolt --prefix $HOME/test-install-bolt
-- Install configuration: "Release"
-- Install configuration: "Release"
-- Installing: /home/aaupov/test-install-bolt/lib/libbolt_rt_instr.a
-- Installing: /home/aaupov/test-install-bolt/lib/libbolt_rt_hugify.a
-- Installing: /home/aaupov/test-install-bolt/lib/libbolt_rt_instr_osx.a
-- Installing: /home/aaupov/test-install-bolt/bin/llvm-bolt
-- Installing: /home/aaupov/test-install-bolt/bin/perf2bolt
-- Installing: /home/aaupov/test-install-bolt/bin/llvm-boltdiff
-- Installing: /home/aaupov/test-install-bolt/bin/merge-fdata
```

Fixes #57249.

Reviewed By: #bolt, rafauler

Differential Revision: https://reviews.llvm.org/D139972