Provide a direct way to pass a custom solc binary path

[dmuhs]

Overview

In some scenarios where I am applying py-solc-x, a user might want to specify a solc version that is already set up on their machine. This means that the automatic installation should not be executed.
I have seen that there is the SOLCX_BINARY_PATH env var, which allows the user to specify which directory to look in for a solc binary. There is also a platform-specific check using which to look for the solc binary on the PATH.
When using the library (which is absolutely amazing btw!), I expected a more explicit way. Please consider the following examples.

Specification

An addition to the compilation parameter set, such as:

solcx.compile_standard(
   ...
   solc_path="/foo/bar/solc"
)

This would effectively short-circuit any internal checks looking for the solc binary and simply take over the parameter's location if it has been set. Alternatively, and following the paradigm of explicit module-level calls, an explicit setting outside of a function call can be considered as well:

import solcx
solcx.set_solc_installation("/foo/bar/solc")

This would result in a global short circuit of the checking logic and always use the path set with set_solc_installation.

At first glance both ways seem to not cause any breaking changes.

[iamdefinitelyahuman]

I really like this! It would essentially reconnect py-solc-x with the original py-solc by making the installation and version management an optional behavior.