7b04fabe2d build: Introduce "Kernel" installation component (Hennadii Stepanov)
Pull request description:
This PR enables building and installing only `libbitcoinkernel`, without the need to disable other targets during the project build system generation:
```
$ rm -rf build && cmake -B build -DBUILD_KERNEL_LIB=ON
$ cmake --build build --target bitcoinkernel
$ cmake --install build --component Kernel --prefix /home/hebasto/INSTALL
-- Install configuration: "RelWithDebInfo"
-- Installing: /home/hebasto/INSTALL/lib/libbitcoinkernel.so
```
Please note, that only the `bitcoinkernel` target is being built.
Related to https://github.com/bitcoin/bitcoin/issues/30801 and https://github.com/bitcoin/bitcoin/pull/30814.
ACKs for top commit:
TheCharlatan:
ACK 7b04fabe2d
ryanofsky:
Code review ACK 7b04fabe2d
Tree-SHA512: eac114dde059e47c91938a4a9108fc0fc693b5342ed3b6ecb971615be8ad3225b9985aae12d6ad18e673edf1bd39a5ecf259c1b61734f221669091bf2ce93a67
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