Support binary headers, metadata, query parameters - 17.5 backport

This is a backport of:

• Various refactorings (!1911 - merged)
• Support passing empty and binary gRPC metadata ... (!1927 - merged)
• Support passing empty and binary HTTP header va... (!1932 - merged)
• Support passing binary HTTP query keys and values (!1942 - merged)

for %17.5.

Relates to https://gitlab.com/gitlab-com/ops-sub-department/section-ops-request-for-help/-/issues/451.

• Support passing binary HTTP query keys and values

https://www.rfc-editor.org/rfc/rfc3986#section-3.4.

Changelog: fixed (cherry picked from commit de9232be)

• Validate proto messages in tests

(cherry picked from commit 3ed4322c)

• Rename EquateHeaderKV -> Equate

(cherry picked from commit fc834a16)

• Extract common code into StringMapToSliceWithBytes

(cherry picked from commit f52eef0e)

• Rename ValuesMapToURLValues -> QueryKVToURLValues

(cherry picked from commit b14568fe)

• Rename URLValuesToValuesMap -> URLValuesToQueryKV

(cherry picked from commit b2178e10)

• Extract buffering logic into Accumulator for reuse

(cherry picked from commit dfb09faf)

• Improve types

(cherry picked from commit 26439df5)

• Support passing empty and binary HTTP header values

https://www.rfc-editor.org/rfc/rfc9110.html#name-field-values.

Changelog: fixed

(cherry picked from commit 12576e86)

• Support passing empty and binary gRPC metadata values

(cherry picked from commit d0dd344f)

• Cleanup function signature

(cherry picked from commit 45137dff)

• Move helpers into separate file

(cherry picked from commit 1c73aedb)