docs: EXPOSED-799 Add migration guide for 1.0.0

[bog-walk]

Description

Summary of the change: Adds a guide for migrating existing users from 0.61.0 to 1.0.0

Note: While the guide mentions R2DBC, R2DBC-specific features are not the highlight. The focus is primarily changes that an existing JDBC user will face, not how to transition from JDBC to R2DBC.

Detailed description:

• Why: No documentation other than some breaking changes related to the beta release have been published yet.
• What:
  • New migration guide .md file added
  • Renamed existing migration guide to be version-specific
  • Replaced existing guide with the new one in home topic.

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Type of Change

Please mark the relevant options with an "X":

• [X] Documentation update

Affected databases:

• [X] All

Checklist

• [X] The build is green (including the Detekt check)
• [X] Documentation for my change is up to date

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Related Issues

EXPOSED-799

[e5l]

@nomisRev, please also check