build: Re-add command to install vcpkg #21733

vcpkg integrate install must be executed so that msbuild will automatically install external dependencies.

It was removed in https://github.com/bitcoin/bitcoin/commit/712f95d3324d02310dd468e7bfd1e1b0df432e77

It was originally added in https://github.com/bitcoin/bitcoin/commit/76445677586a4c2fa72606b662269a4390c2e71f

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ACK

ACK de17d245b7462784f9d36591b0f346aa6b2e9b8c.

I did shorten the vcpkg instructions when manifests were introduced. The idea being that msbuild would take care of calling vcpkg to install the dependencies automatically and it would be one less step.

Given that:

• It seems to be recommended to still call vcpkg integrate install even with manifests enabled.
• At least one issue, #17864, has been raised with the Bitcoin Core vcpkg instructions.
• Executing vcpkg integrate install should not cause any problems for manifests (although it's not clear what happens if different versions of a dependency are installed in the main vcpkg directory and the manifest directory).

It's an ACK from me.

ACK de17d245b7462784f9d36591b0f346aa6b2e9b8c, I use the same in #21551.

Sorry, I missed the "Merge message contains an html comment!" warning when merging this. So the merge commit now contains an html comment.