Define boost::system as header-only component

[klimkin]

Specify library name and version: boost/1.77.0

Use boost_system as header-only library

Starting v1.69.0 Boost.System is header-only. A stub library is still built for compatibility, but linking to it is no longer necessary.
https://www.boost.org/doc/libs/1_75_0/libs/system/doc/html/system.html#changes_in_boost_1_69

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[ghost]

I detected other pull requests that are modifying boost/all recipe:

• boost: fixed stacktrace_windbg* components, improved stacktrace test. #7281
• #7244 numa option is deleted if Boost fibre is disabled #7248
• [boost] Apply patch to fix https://github.com/boostorg/graph/issues/268 #6132
• [boost] For Visual Studio, pass some values of settings.compiler.toolset to B2 #5119
• boost: use clang-win toolset when compiler=Visual Studio and compiler.toolset=ClangCL #4749

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[conan-center-bot]

All green in build 4 (984471194a5b1117f73ef53e41d5a0a6b3c34a14):

• boost/1.69.0@:
  All packages built successfully! (All logs)

• boost/1.70.0@:
  All packages built successfully! (All logs)

• boost/1.75.0@:
  All packages built successfully! (All logs)

• boost/1.71.0@:
  All packages built successfully! (All logs)

• boost/1.72.0@:
  All packages built successfully! (All logs)

• boost/1.73.0@:
  All packages built successfully! (All logs)

• boost/1.74.0@:
  All packages built successfully! (All logs)

• boost/1.76.0@:
  All packages built successfully! (All logs)

• boost/1.77.0@:
  All packages built successfully! (All logs)