fix: correct versions with prereleases

[reggi]

prereleases do not work in release-please, i'm seeing the inability to get a repo into or out of prerelease mode, (where the packages have tags in the versions ie. -pre-0 at the end).

• I was unable to get a repo into prerelease using the latest version of release-please on my personal project reggi/packages.
• And the npm/cli has been stuck in prerelease mode. It was able to get itself into prerelease because of the wrapper around release-please we have in this repo. (trail: npm/cli workflow, Strategy Turnery)

I do not believe release please has this options.prerelease ternary anymore here's the mapping of what versioning-strategy is uses.

And even if it did choose to use PrereleaseVersioningStrategy or DefaultVersioningStrategy neither of these strategies have the ability to leave a prerelease. Because they always add the current prereleaseType or prereleaseType from the config from the existing version. Neither of these classes even have access to the options.prerelease boolean.

I created a fork of release-please which would deprecate the need for this PR, https://github.com/reggi/release-please with the typescirpt / esm alternatives to the files included in this PR:

• https://github.com/reggi/release-please/blob/main/src/versioning-strategies/semver.ts
• https://github.com/reggi/release-please/blob/main/test/versioning-strategies/semver.ts

This is added as a new versioning-strategy semver. To note the property currently documented as versioning-strategy in the docs is not working, and is currently versioning. I opened a PR to fix the json schema for the config, but now we know it's a bug i'll leave that discussion open there.

So "versioning-strategy": "semver" would be ignored and you'd need "versioning": "semver", again not relevant to this PR but another quirk to note.

This PR replaces both strategies with a new SemverVersioningStrategy which is always used, and has prerelease-aware replacement for semver.inc

• Given the existing functionality for semver.inc, when incrementing to preminor with 2.1.0-pre.1 it bumps the minor 2.2.0-pre.0 which is incorrect.
• The inc function included in this pr takes 2.1.0-pre.1 and sees that patch is 0 and will assume a bump has already taken place because it's in prerelease, and will only increment the tag number (known in semver as identifierBase or n) to 2.1.0-pre.2.

We will most likely also have extended conversations about adding this new prerelease-aware functionality to semver.inc in some way so other projects such as release-please can properly implement prereleases.