[DB-15464][Sizing Calc] buffer to choose higher vCPU instance type

[shaharuk-yb]

Describe the changes in this pull request

Pre-calculate the required number of cores and use it for selecting the appropriate instance type recommendation.
Current sizing calculator decides final recommendation based on the number of nodes required in later stage( which is calculated using the required number of cores in the first place). Hence, the better way is to use required number of cores.

example: Take into consideration following two sizing recommendation are suitable.

• 8 vCPU setup needing 296 cores gives 37 nodes.
• 16 vCPU setup needing 290 cores gives 19 nodes.
  But, currently, in pickBestRecommendation, while recalculating the cores, it uses nodes * vCPU. Thus giving,
  8 * 37 ==> 296
  16 * 19 ==> 304
  Even though the required cores were 290 but because of reverse calc, it says 304 cores required for 16 vCPU setup and hence current sizing calculator suggest 8vCPU setup as it favours lesser cores(even though the number of required cores originally were higher).

This change directly considers required cores instead on recalculating it. Giving better recommendation.

Describe if there are any user-facing changes

NA

How was this pull request tested?

Manually and with CI jobs.

Does your PR have changes that can cause upgrade issues?

Component	Breaking changes?
MetaDB	No
Name registry json	No
Data File Descriptor Json	No
Export Snapshot Status Json	No
Import Data State	No
Export Status Json	No
Data .sql files of tables	No
Export and import data queue	No
Schema Dump	No
AssessmentDB	No
Sizing DB	No
Migration Assessment Report Json	No
Callhome Json	No
YugabyteD Tables	No
TargetDB Metadata Tables	No

[sanyamsinghal]

LGTM. Thanks for the clear PR description.